Well, Viktor, this is an interesting experience. I suppose a reasonable place to begin would be back at the beginning. I think people will certainly be interested in how your career started and how you got into this field and what things were like in those bygone days.
I got into the development of the nervous system through my doctor’s thesis. Perhaps I have to give a little bit more background. I went to Freiburg in 1919 to study with [Hans] Spemann who was then considered to be one of the outstanding experimental embryologists, although he was not yet very widely known. After a few semesters I asked him for a thesis. At that time there were no other formalities; you didn’t have to complete any course work or anything like that. You didn’t have to take any prelims – you just asked for a thesis and if the professor thought you were ready for it, he gave it to you. So that’s what happened.
At that time he and half a dozen graduate students and post-docs worked on what later became known as “the organizer.” Since he had my academic future in mind, he thought I should have a completely independent topic, for which I would get credit independently of the work on the upper lip of the blastopore. He put it this way: “There are already too many people hanging on the upper lip” and I should start somewhere else. Apparently he couldn’t think of much else, so he suggested that I repeat or check up on some rather improbable results which somebody else by the name of Dürken had obtained. He contended that if he extirpated the eyes of a frog embryo, then not only would the eye be missing but the legs would also be malformed. He showed pictures of that in his paper and he developed a rather far-fetched hypothesis that the whole business was neurogenic. That means that the absence of the eye would interfere with the development of the mid-brain and the mid-brain defect resulting from that would be felt all through the spinal cord, and eventually the nerves going from the spinal cord to the limbs would be abnormal, and as a result the limbs [would be abnormal].
So I did many hundreds of experiments and at first, lo and behold, I got some limb abnormalities in a very small percentage of cases following the eye extirpation. It turned out later that was an accident, that it was probably due to something in the water in which we had the animals – some trace elements of zinc or something else. It had nothing to do with the nervous system and with the operation. Eventually, after a few years [and] after I had done a thousand or so eye extirpations, I just began to face the problem of whether the nervous system has any influence on limb development in the frontal attack. But that’s another business – that’s the way I got in.
So what came of the thesis?
I published a thesis in which I said that out of a thousand only five or ten percent malformation was very unlikely and I tested all possible explanations, for instance, that there would be species in Germany that would respond differently from each other. I explored that and found that whether they were from north Germany or south Germany they behaved exactly the same way.
So theses weren’t too much different then than now. Who were some of the others at that time in Spemann’s lab?
There was his first assistant and oldest student, Otto Mangold, who took his habilitation at that time, which means that he had to present a paper and a lecture to be admitted to the faculty. That happened while I was there. He was very active; I don’t think he was very original but he was very much liked by Spemann and very much promoted by him. He became later his successor at the Kaiser Wilhelm Institute in Berlin as the director of the Institute for Experimental Embryology and eventually became the successor of Spemann when Spemann retired, in 1939, I think. There was another man whom Spemann instigated to do some experimental work on amphibians, but who was really the honeybee man, a man who was much more interested in honeybees and their culture and pollination and that kind of thing, and who eventually established a research institute for honeybee science and gave up experimental embryology altogether.
There were some others who taught other things. At the very beginning, for the first year when I was there, there was a Swiss, Fritz Baltzer, whom he had known in Wurtzberg at the laboratory of [Theodor] Boveri where Spemann grew up. And Baltzer was also a student of Boveri and he had a very profound influence on me and later on, after he had moved after a year to take over the directorship of the Zoological Institute in Bern, became a close friend of mine. He continued a slightly different line of research which dates back partly to the influence of Boveri. He combined genetics and experimental embryology in a very ingenious way. He had a lot of students, among them Ernst Hadorn, whom you probably know, who became very famous later on for his work on Drosophilia.
What about Spemann himself? What kind of a person was he to work for?
He was different persons. He was very different at the time when I was a student, when I was a graduate student from 1919 to 1924 or 1925. And then I went away and came back as an instructor at his institute, at his invitation, and became a staff member and went through habilitation. And then we became fairly close and I got to know him very much better and a friendship developed to the extent that the generation gap permitted that. He was always very friendly and helpful, although I must say that with his Ph.D. students he used the sink-or-swim method. The only advice I got during the two years I worked on my thesis was when I asked him whether a very particularly important embryo should be fixed or whether I should wait for a day or two, he said “I am glad that I don’t have to make that decision.” So that was maybe advice for the future to apply to my own students. But he never interfered – he never gave much advice. He never told me what to do or what not to do. In that respect he was very reserved.
He did give you the thesis; you were assigned that project.
Yes. I didn’t know anything about that. Later on, all of my future work developed out of that beginning; I developed it myself. And he took very little interest in it because his interest was very strongly focused on the very early development and mine started when his interest ended.
What was your perception of his important work as it was going on?
I thought it was extremely important. These were years that led to the organizer experiment. So I lived through all the excitement that culminated in the experiment which was actually completed, where the data were out in 1922, although it was published in 1924 by Spemann and Hilde Mangold. So I lived through the excitement of these years and [it] was perhaps the most [exciting]; except for the beginning of the NGF [nerve growth factor] it was by far the most exciting period, although I was a bystander.
What was the relation between Spemann and Mangold?
Very close. They worked very closely together, they published together, they planned experiments together on which Spemann, when Mangold moved to Berlin-Dahlem, Spemann kept very close track.
Was she a post doctoral fellow?
No, he. Otto Mangold. Then Otto Mangold became director. He kept very closely in touch with Spemann and everything was planned together.
No, I mean Hilde Mangold.
She was the graduate student who at the last moment, after another topic failed to give results, was assigned the experiment which later got to be known as the organizer.
That’s what I’m interested in bringing out: whether her role in the organizer—
She was merely a graduate student who did what she was told and she labored on it and at the very end of the breeding season in 1921, I think it was, she got this famous embryo which showed that if you transplant an upper lip to the flank of another embryo you get a secondary embryo. Everybody got extremely excited and then she was supposed to produce more. But it was so difficult to do these experiments, and since we didn’t have any antibiotics, they died by the hundreds, literally. And out of a very substantial work of several hundred operations, five were published.
So all that work is based on five embryos?
Yes. And a few years later when [Johannes] Holtfreter developed the necessary techniques, you could raise these embryos by the dozens to much older stages. But the essential results and conclusions were drawn on these five embryos, and Spemann wrote the paper.
So Holtfreter came into the lab somewhat—
He came simultaneously with me. We worked in the same room for several years, except that we had different working times. I worked during the day and he worked during the night so we didn’t see much of each other.
And what was the whole evolution of his work and how was it received by Spemann?
Well, he got an even more remote doctor’s thesis, about the liver of the amphibian embryo, which amounted to absolutely nothing except that it granted [him] the Ph.D. Then he went traveling around the world and doing all kinds of things – being an artist – and very late, three or four or five years later he decided to go back to science. He was ready to teach. He was ready to take a job as a supervisor of an oyster station on an island, and then when the position which I had with Mangold in Dahlem, [the Kaiser Wilhelm Institute for Biology in Berlin-Dahlem] became vacant because I moved back to Freiburg, he was offered that job. And that’s the only reason why he stayed in science – that I moved away. So I made room for him, and the years which followed, from 1929 to 1933 were by far his most productive years. But then he got into trouble with Spemann because he made discoveries which—
Yes, I think people are curious about what that must have been like. After all, a discovery that more or less questioned the major work of the mentor—
It was a very delicate situation because he worked in the laboratory of Spemann’s closest collaborator and friend and had hundreds of experiments which proved that the dead organizer can induce, if anything, better than the living one. And that had not been agreed upon between Mangold and Spemann. Holtfreter never kept it secret, so it filtered very soon through Mangold to Freiburg what happened. And then Spemann suddenly discovered that his favorite student, Bautzmann, had also had one or two embryos that had been exposed to some kind of a killed tissue and produced some neural enlargements – not real embryos. And somebody else had – Mangold had a very dubious case. And Bautzmann, who was in Hamburg, had this case. So, Holtfreter traveled to Bautzmann at Spemann’s request, I think, to straighten out these things and find out further and so on. And it turned out that Bautzmann had two or three cases, and so on.
He didn’t fight this evidence—
He didn’t fight it, but it was agreed [that] Mangold also had a dubious case. Neither Bautzmann nor Mangold published it because they didn’t think they had much, quite correctly. So Spemann, in his best diplomatic way, arranged for a four-man report in Naturwissenschaften [20:971,1932], which appeared in 1932, in which Bautzmann and Mangold reported their more than dubious cases, Spemann reported an equally dubious case, which one of his students had had, and Holtfreter came out with some fifty or so cases.
I just found a letter from Spemann recently which he wrote me in 1932. He was delighted that this potentially explosive issue had been settled in such an amiable way. That means [that] Holtfreter had been beaten down to consent, instead of publishing what he had, to put his name on the four-man paper. So it wasn’t quite aboveboard.
What was your impression of Spemann’s more personal reaction to that. He must have been very—
No. He accommodated, as a scientist would do. I mean, you can’t fight facts, particularly if they are so terribly impressive as the ones that Holtfreter had. So he made the best of it and pointed out that from the beginning he had neither had an organizer theory and always had insisted that the reacting system would be at least as important as the stimulus. So he made the best of it, and in his book which he wrote at that time, and which appeared in 1934 – it was about the worst time to write a book about it – but he made the best of it.
This is a very complicated issue; you’ve talked about it before. Looking back on all that sequence of events from the organizer experiment through the publication of this four-man paper, what do you regard as the upshot of all that? I guess the question I’m really asking is how should people regard Spemann’s contribution in the light of the key experiment?
I think the substance of the key experiment stands completely uncontested. The subsequent results made it extremely difficult to interpret it, but the time hasn’t come yet to really tackle it. There has been an awful lot of efforts to identify and isolate a chemical substance which would do complicated things, and I think that has been done, although the biochemistry may not be the best. But the whole business, of course, has gotten lost because the phenomena which we are dealing with in the organizer experiments are supercellular events on the level of organization which, at the moment, is completely inaccessible to analysis. Molecular biology, cellular biology and subcellular biology have wiped this whole problem off the map.
For the time being only, one hopes.
Yes.
Let’s come back a bit to the nervous system. This is all really embryology that we’ve been talking about. So what were the events that led you from embryology to neuroembryology?
For about twenty or twenty-five years I was an embryologist who attended the meetings of the embryological societies and was a full-fledged member. I was even the president of the Society for Developmental Biology for several years and I happened to work on the nervous system just as other people happened to work on the heart, or you name it. The emphasis on “neuro” really did not come until Rita [Levi-Montalcini] came in 1949.
Maybe that gets ahead of the story. What happened – it would be interesting to say a little bit about what happened in the 1930s and how you came to leave Germany and how you came to Washington University.
OK. The only thing that made me different from most other embryologists is that I asked some very specific questions about the kinds of interactions between embryonic structures which were generally considered as inductions: lens induction, ear induction, and so on. So the basic problem that was being discussed in the 1920s and 1930s was interactions between embryonic structures. The obvious thing which characterizes the nervous system – makes the nervous system unique – is that it’s connected with target organs, and you can ask the question, “What does happen if you remove the target organ; what happens to the nerve centers? If you remove the nerve centers what happens to the target organs?” It was in the general framework of correlations in embryonic development, applied specifically to the nervous system. So, from the beginning I had these two questions: the one question – what happens to the target if it doesn’t become innervated I had resolved already in 1928 by showing that if you let a limb off an amphibian grow without innervation, it has never seen a nerve, it will grow normally, develop normally. So that aspect was already resolved.
That was really your first independent work as an instructor?
Yes. And that was decisive. I mean, that was crucial and there was never any doubt about it – nobody has ever touched it again except myself with the chick embryo. So what was left was the reverse. That I started when I came to Chicago and that was an extremely fortunate coincidence, because when I had to leave Germany – I didn’t have to leave – I mean, I left on a Rockefeller Fellowship in 1932 when the signs were on the wall but no decision was made.
So your acceptance of that fellowship had really nothing to do with the situation? You would have come anyway?
No, I would have come anyway because Spemann had been in Woods Hole in 1931, had befriended Lillie [Dr. Frank R. Lillie] and [Edwin Grant] Conklin and all the others in Woods Hole; came back, and when the Rockefeller representative came to Spemann to ask whether he had somebody to give a Rockefeller Fellowship for the United States, he suggested me, and at the same time [he said] his friend Lillie was the person with whom I should work. And that was extremely fortunate because Lillie was the only laboratory in this country that worked with chick embryos, and in 1909, that means twenty-two years before I came here, he had a student who had tried to kill wing buds in the chick embryo to see how the nervous system was reacting. How Lillie ever got that idea I don’t know. Then, Miss [M. L.] Shorey, who did it, disappeared from the literature so I couldn’t ask her either. So Dr. Lillie and I agreed to repeat the experiment in order to try out my glass needle technique. That was the assignment I had from Spemann and the Rockefeller Foundation – to apply the glass needle technique of Spemann to the chick embryo. So the obvious thing to do was to repeat the old Shorey experiment.
Was Lillie just a sort of bystander in that or did he really have an active part?
Oh, for heaven’s sake. Lillie was one of the most important statesmen in Chicago. At the Chicago University he was dean of the medical-biological faculty and was sitting in the hospital in his office and he was, I think, also president of the National Academy or Research Council – I don’t know these details. But he was 100 percent busy and the only time I ever saw him, really, was in Woods Hole in the summer. So I was entirely on my own and I was turned over to Dr. Willyer(?) who was the embryologist in the zoology department. He had as his right hand the lady who got her Ph.D. with him, Mary Rawls, who knew everything that anybody knew about handling chick embryos. I was turned over to her and I picked up from her what I could and in a few months in some respects, I was ahead of her.
At what point did your conversion from the amphibian to the chick take place?
At the moment I entered Chicago.
But you had no preconception that it would be nice to move on to the chick? This was just happening?
No. It was a one-year proposition.
Then what events led to your not returning [to Germany] and to coming to St. Louis.
After I had been in Chicago for five months or four months, Hitler came to power. Spemann wrote me a letter that I couldn’t come back – he couldn’t do anything about it. He had orders from above not to appoint anybody or to dismiss anybody who had any Jewish racial or Jewish history. The fact that I was a Protestant didn’t count. My parents were racially Jewish and that was it. Fortunately, the Rockefeller Foundation immediately started an emergency relief program for displaced scholars, as they called it. I was on top of their list because I was already a fellow. They supported me for three years until I came to St. Louis.
So Spemann’s behavior in all this was – how would you characterize it?
Well, he had no choice. What his feelings were I don’t know. I have quite a few letters from that time. He regretted to lose me and so on and so forth. At that time I think he still had hopes that Hitler would save the German people from their terrible economic and political doldrums in which they had fallen. He never mentioned anything political in his letters, but he certainly expressed his personal feelings.
So from the personal point of view he was well-meaning but politically, perhaps, naive.
I think nobody could have done anything different. He couldn’t have fought it, you know, even if he had wanted to. In other respects he might have shown more resistance, but as far as the relation to me was concerned it was absolutely correct and nothing else could have been done.
And then from Chicago to St. Louis – how did that come about?
Well, they needed biologists. They had some very shrewd people; we refugees were available for a bargain. I made such a bargain. He came, a very shrewd and very pleasant dean who had plenty of time – because he was a professor of Latin – came and looked me over and I came in April 1934 for a meeting to St. Louis and was looked over by other people including [Carl] Cori and others. And then I was offered the job and I moved in 1935.
Did you have in mind coming here [and] setting out on a new line of work?
My assignment was to establish a strong program in experimental embryology. At that time Frank Schmitt was the major operator in the department. He was not yet chairman, but he became chairman while I was here and we cooperated very strongly. He became extremely interested in embryology and I picked up some bits and pieces of what at that time was [the] forerunner of molecular biology. He was really one of the pioneers; he had somebody who worked on x-ray diffraction of nerves and nerve membranes.
I think it’s worth emphasizing that he was just not appreciated. He was really a remarkable—
At that time he was truly productive and creative and forward-looking. He was certainly one of the most forceful pioneers – forerunners of molecular biology. No doubt. In fact, we published a paper together.
What were the experiments of those days when you first came here in the mid-1930s?
I published a lot of material which I had accumulated in Chicago, particularly transplantation. The new thing was transplantation. The real thing that I claim credit for is [that] I’ve made the chick embryo available for very complex and a great variety of experiments which were formerly not possible because the technique of using glass needles wasn’t applied. I exploited everything that could be done with respect to limb transplantation, particularly the problem of whether nerves were necessary; then the effect of limb extirpation on sensory ganglia and motor system. And the problem in which I had become interested with amphibians in the early days was how nerves find their way to their targets.
Then I became interested in the early phases of motor column differentiation, methodic patterns – I discovered that the ventral part was ahead of the dorsal part and so on. And then in 1947 Rita came. So in these years between 1932 when I came and 1947, I think there were only a handful of people who worked on the nervous system. They were all embryologists who happened to work on the nervous system. I was practically alone. [Samuel] Detwiler was the only big figure who worked at that time. He helped me a great deal; he promoted me very much. He invited me to one of the first symposia. At that time symposia were invented. Believe it or not, when I came there weren’t symposia. The Growth Society was one of the first two or three societies that invented symposia. Paul Weiss was very instrumental in that. Detwiler invited me to a symposium in Cincinnati – I remember that quite vividly – and promoted me very much. So I got grants from the Rockefeller Foundation and so on.
The way in which Rita [Levi-Montalcini] came is known to a lot of people, but it may be worth describing.
She read the first paper I wrote in Chicago, which was published in 1934 on the effect of wing extirpation on the motor system. She read it during the war, I think in 1940, ’41, [or] ’42 and under very difficult conditions she repeated the experiment, together with her teacher, preceptor, mentor, Giuseppe Levi. There are several papers of Levi and Levi-Montalcini on the effects of wing extirpation on the sensory ganglia. She came to entirely different interpretations of the results, which were identical. Since I never have indulged in controversies in public or in print, I thought to settle that by repeating the experiments together and see what we got. So I invited her to come to St. Louis.
How did that turn out?
It turned out that she was right, as usual, in her interpretation. But then we became interested in going on from there.
Let’s talk about that. How did that whole business start, of your mutual interests?
When we planned a program it wasn’t just repeating the wing extirpations. We wanted to really do a very comprehensive job so at the same time we planned to do wing extirpations and transplantation of additional wings. As you know, the wing extirpations gave some fringe benefits, namely the discovery of naturally occurring neuronal death. But you don’t want to talk [about] this.
Yes of course.
O. K. That was the one. First of all, we showed that indeed, the spinal ganglia became smaller when the wing was missing and her idea that this was due to a secondary degeneration of cells which had already differentiated without the influence of the limb, was correct. That means it was a regressive process rather than a progressive process as I had guessed, wrongly. And then she discovered the naturally occurring death in spinal ganglia which had not been affected by the operation – which we are on the same series of slides. So she went down the slides and found that these degenerating cells, which were very prominent in the wing-innervating ganglia were also present in the thoracic ganglia.
It’s amazing [that] this was missed since so many people must have looked over the years.
You would be amazed how difficult it is to really see things when you look at things. For instance, since the beginning of the nineteenth century people have looked at spinal cords, and I was the first one to really see that at a certain moment all the mitoses are almost exclusively concentrated on the ventral half and two days later they are all concentrated on the dorsal half and there is nothing on the ventral. Hundreds of people have looked at that because that was the object of all embryology courses all over the world. Every instructor who taught students to look at the spinal cord of chick embryos or pig embryos looked at it but didn’t see it. No, it’s very difficult. So she had an eye on it. To me this is one of the characteristics of Rita’s genius – to see things which nine out of ten others would not notice.
Then very soon we became much more interested in the hyperplasia, so-called, of the ganglia which had to innervate two legs or two wings instead of one – overloaded, as Detwiler called it. So we concentrated all our efforts – for us much more miraculous than death – growth is more interesting than death. So the discovery of naturally-occurring death really became dormant for ten years until some amphibian people picked it up. We went ahead with the investigation of why or in which way do ganglia become large.
But you were aware that the naturally-occurring death was a critical discovery – or was that—?
No, it wasn’t. We weren’t.
So that came only later?
Yes, other people made a big – I mean, it became a media event much later.
But things can become media events much later and still be recognized as important events by the discoverers at the time.
Quite frankly, I must say [that] at that time when I wrote the paper, and I know that I went into a great analysis and proposed a hypothesis of competition and so on, but didn’t follow up. I was fully aware of what it was, but the interest in the enlargement of ganglia was so much greater – fortunately.
Yes, sure. It paid off handsomely.
It paid off better – or it paid off earlier.
So, how then did those events unfold, leading from the interest in hyperplasia to [Elmer] Bueker’s experiments?
At that time, everybody began to think in chemical terms. There must be a chemical trophic factor in the wing that nourishes the ganglia and prevents them from dying. That much was clear, so the obvious next thing was to see whether there couldn’t be a way of identifying the chemical agent. We knew that we couldn’t get anywhere— First of all, we didn’t have a biochemist at that time. Second, we knew enough to know that you couldn’t get, by any chance, enough material out of a hundred or [even] a thousand wing buds. So we started to implant liver and all kinds of other materials into the celomic cavity to get bulk, eventually. If liver worked, then we could extract something out of a big liver.
So you were just implanting various things in the hope of finding a large tissue that would stimulate the hyperplasia?
Correct. That didn’t work. And then I showed Rita the paper of Bueker, who had, two years earlier, gotten this very interesting idea of transplanting a mouse tumor into the celomic cavity for the same reason. And he had gotten a slight hyperplasia, but not anything much better than what the liver would do. And to his eternal regret, he moved to something else and when we asked him for the right to repeat that experiment he said, “Yes.”
Was he still in your lab?
No. He was an older person who was a high school teacher in U. City [University City] High School and had published on collembolan. You know what collembolan are? These are primitive insects. So he was a specialist on primitive insects when he started, and all he wanted was a Ph.D. He was a very ambitious person and a very stubborn person. He came to me and said, “I want a Ph.D. I can work only on weekends and in the summer.” And I said to him, “I don’t know anything about insects. If you want to get a Ph.D. you have to work on the chick embryo.” So he worked on the chick embryo and wrote his Ph.D. thesis, a very nice piece of work, but not dealing with sarcoma. It was not my idea, it was his idea. So that was a follow-up of his Ph.D. thesis when he was already at Washington, D.C.
I see. I didn’t know this. When you say it was his idea, it was his idea in the sense that he used sarcoma, but he was following the general plan of seeking the bulky tissue—?
Of course. I cannot remember and I do not know whether this idea came about in discussions with me; it would have been very obvious to discuss this topic just as I discussed it with Rita. But he had the idea and nobody has contested that. He had the idea to do it, he did it, he described the results.
He did this in Washington?
I don’t know where he did it. He was first in Columbia, Missouri, and then he moved to Virginia or Washington, I don’t know. At any rate, he did not do it here and I didn’t know about it – well, I don’t know whether I knew about it before, but I just had the reprints. Rita had the reprint and we decided since we were unsuccessful with our efforts— And then we got the mouse sarcoma 180 and 37 from Bar Harbor, I think.
Which were exactly the ones that he had used?
He had already found – he did find either at that time or later that carcinomas don’t work. So we used the ones that worked – we had three – sarcoma 137, 180 and 37 – and settled on 180. The earlier works were done with 37 and the 180 there was no difference. But Rita got the same results except on a much larger scale – the results were much more spectacular. Rita very soon had the idea of improving the technique by transferring the sarcoma in the chorioallantoic membrane of the chick embryo for several transfers, several passages, to get the tumor adjusted to the chick.
Whatever that means.
Whatever that means – but it worked – or we got much more powerful sarcomas than Bueker ever had.
You didn’t do anything really different?
Well, that was different. She didn’t take it out of the mouse into the chick embryo but did transfer passages for several weeks.
And the nervous systems in successive chicks were progressively more affected by the—?
No. There was no great effect. At any rate, that was the standard technique that we used. And very soon she found the first look at one of the most dramatic embryos was that the sympathetic chain ganglia were, if anything, even more enlarged – so much so that the chain practically was transformed into a rope.
This is amazing – that such a strong effect was achieved with this.
Yes. To this day our contention at that time that part of that story is an increase in cell numbers is not yet settled. It could all be just enlargement. Then this thing unrolled by itself, and an interesting thing came: after we had the bulk, we needed a biochemist. So we talked to Sid Velick [Sidney F. Velick], who was the professor of biochemistry in Cori’s department, here. He was the protein chemist. We invited him and showed him the preparations and asked him whether he would cooperate with us. He looked at that and thought for a day and then he said, “No, it’s hopeless.” He wouldn’t touch it. Then we were looking for somebody else. Martin Kamen happened to be here; I don’t know with whom he worked. He was a great friend of Rita and me, too, and he belonged to the Kornberg-Mel Cohn group that was all one big group of friends: Hogness [David S. Hogness], Kornberg [Arthur Kornberg], and so on. He said he had a post-doc who didn’t have a job who would, perhaps, be interested – and that was Stanley Cohen.
This was in 1955 or so, then?
No. It was in 1953, perhaps. So, Stanley Cohen came over and he took the job and within a few months he had a nuclear protein which worked, extracted from the mouse sarcoma. It worked. But he didn’t know whether it was the nucleic acid or the protein, so he asked Kornberg what to do. Kornberg said, “Use phosphodiesterases, which you get out of snake venom.” So we ordered snake venom. Then, we found that that increased the effect very considerably – enormously. Unfortunately, he made the control experiment and injected pure snake venom and it went up a thousand-fold compared to the purest extract he had from the mouse sarcoma.
How was he working in those days, doing those experiments? Was that done by himself, more or less, or directly with Rita?
No. He had his own little biochemical outfit; I know nothing about it, with the Sephadex column – whatever one did at that time. I didn’t have the remotest idea; didn’t even become interested in it. To this day I have stayed away from test tubes.
I sympathize.
Then, of course, Rita and he got more and more involved in developing one problem after another and then he had the brilliant idea of A) using the antiserum to prove the proteinic nature of his agent – and got the immuno-sympathetic— The other brilliant idea was, since we worked on a very low budget, to reduce the expense of snake’s venom by using the salivary glands of male mice, which were cheaper than snakes and cheaper than female mice.
So that was the motive for looking at the mouse – just economics.
Well, yes. Also, it was obvious that it would be much simpler to use mice, because it came from salivary glands. I mean, that was his idea. And we used male mice because female mice, as you know, are more expensive.
I didn’t know that.
Sure – they reproduce. Pregnant female mice are more expensive than non-pregnant females. It was all a matter of dollars, but at that time we didn’t operate on a $100,000 budget. He was lucky enough to get male adult mice because neither young male mice nor female mice have the NGF in any appreciable amount.
Nor rats.
Very little. So if he had settled on rats, it wouldn’t have helped very much. So he hit by serendipity exactly the right material. As you know, to this day the male adult mouse salivary gland is the bulk.
One thing I’ve always been curious about is why in this period, when NGF was taking off in many respects, your involvement in it decreased rather than increased.
To be quite honest, first of all, I could not participate in the biochemical turn it took. And second, I wanted to give Rita the credit. I was quite well-known at the time; Rita was a completely unknown. On the other hand, I recognized fully her tremendous share in the whole sequence of discoveries and I felt that she should get the full credit for what she was worth. So I wouldn’t want to stand in her way. But also, I was less and less interested and involved in the biochemical trend that it necessarily, I mean inevitably, took. I’ve never done anything that I wasn’t interested in. So I wanted to do something else which interested me. And then I got involved with this motility [and] opened a new chapter in that.
Say a little bit about the motility, because I think of the various things that you’ve done that’s probably the least well-known and appreciated.
I regret that, because I think that’s the one in which I would claim the most originality and the exploration of an entirely new chapter. I wasn’t successful in putting it on the map but that doesn’t mean that it doesn’t have a fundamental, intrinsic importance.
Amplify on that – I mean, why do you think that is?
Well, the question of how animal behavior develops has obviously been on the minds of people, and as anybody who has come in contact with psychologists knows, they operate very differently from other scientists, namely from premises, from theories, from speculations, from hypotheses, from preconceived ideas. And the preconceived ideas which then later on were experimentally “proven” (quotation marks) were the ones that there’s tabula rasa at birth. That neither nerve connections nor synapses nor anything is organized; everything becomes organized by experience, by learning and so on. It was the one extreme, and the other extreme was that experience and learning have nothing to do with the early phases of neurogenesis; that the right connections are made in form of reference to function and so on. So I thought it was an extremely important decision to be made experimentally. And since I was not a psychologist I could be completely unprejudiced and tackle it with my methods of experimentation. I could extirpate, I could make embryos with no sense of input.
[Interruption in taping]
You were talking about motility.
There were not only these two polar differences in approach – in the theory of how behavior originates. There was also a very inferential and extremely interesting person by the name of G. E. Coghill, whom I had the good fortune to meet in Woods Hole in the 1930s and from whom, incidentally, I inherited an extremely good technician, who took an intermediate position and who had another very interesting prejudice or idea, which was very well-founded on his observations on the salamander _____(?), namely that all behavior from beginning to end is integrated, from the first swimming movements to food intake and so on. Swimming, walking, food intake were all integrated and that local reflexes developed secondarily by what he called individuation and segregation from the total pattern. For many years he dominated the field and everybody, including people who worked on human fetuses, tried to replicate the total pattern.
When I started, I was fully aware that there were three possible solutions to the problem; three prevailing but entirely different and mutually exclusive ways of looking at it. To me, it was an interesting problem – how behavior develops. I had all the tools and started on the chick embryo and the first thing I did was to look [at] what actually happens, which apparently nobody had done. As I said before, first of all, the chick embryo was not particularly exciting, and second, they had preconceived ideas so why would anybody look at what really happens if they know already the outcome? That’s not quite fair because people made observations. The mammalian people were quite sure that Coghill was wrong and that the local reflexes came first and so on and so forth. But there was a chaotic situation and a complete conflict of everybody against everybody else. As a matter of fact, when I took it up in the 1950s, it had been dormant for 10 or 15 years; nobody touched it because there was an impasse.
So what I did was first to look at what the embryo actually did from the first beginning to the end. I looked at it as an embryologist. I hired a man who came from psychology, because I wanted to be absolutely sure if I worked on behavior that I don’t fall into any trap and that I have some competent person who has studied behavior. He also knew statistics in which I’m very weak. I knew that probably statistics would help. So I engaged a man by the name of Martin Balaban, who came with his family, and we worked for two years together. The first thing I saw was (A) that there’s nothing of the Coghill kind of integration except in the first day of movement. It was completely uncoordinated behavior where any part of the body could move while any other part either moved also or was not moving. The second thing we observed immediately was periodicity – that the embryo was constantly in motion for a minute or two and then suddenly became completely inactive, and then took up again.
The third thing we observed was the rediscovery of something that had been observed in 1885 by a very outstanding German scientist, psychologist, and physiologist, William Preyer, who in 1885 had published the first book on the physiology of the embryo, in which you find an absolutely unparalleled collection of data on everything that concerns embryos – pig embryos, human embryos and so on. He also later published a book on the behavior and development of his son from the day of birth, which later on was repeated in Hamburg and led to Piaget. So he was the precursor of me and of Piaget. He had observed that in the first three days of movement of the chick embryo, they started incubation day 3-1/2, so from 3-1/2 to 7-1/2 days of incubation you find this kind of movements – spontaneous we called it, he called it a little differently. I called it “spontaneous motility”; it was independent of sensory input. No amount of scratching or tickling or stimulating would produce any movement during an inactivity phase. He had discovered a pre-reflexogenic period in the chick embryo lasting for three days. That was the third thing that we did and repeated and found very convincing.
So we knew that the people were wrong who preached total integration from beginning to end. We knew that the people were wrong who attributed all beginning of behavior to sensory input, and we had established what Preyer knew: that the central nervous system in an early embryo can generate motility – action potentials – independently of any sensory input. We stressed very much the periodicity, which gets lost at thirteen, fourteen days. The embryo becomes so active that it almost continuously moves. But up to thirteen days there is this periodicity. We stressed that. We stressed the lack of coordination of parts and the spontaneous motility. And to this day I believe that the complete neglect of neurophysiologists of spontaneous motility – except in REM sleep is completely neglected – it may have something to do with the spontaneous activity in REM sleep.
The obvious, crucial and crowning experiment, of course, was to de-afferent the whole egg, from beginning to end and to show that motility in the embryo is not only self-generated, or whatever you call it – spontaneous, between days 4-1/2 and 7-1/2 but throughout the whole period until hatching comes, where integration is needed. So Eleanor Wenger did this very complicated and very difficult experiment of completely de-afferenting the region of the spinal cord by making a gap in the anterior spinal cord so that no input can come in from rostral of the brain and cutting off the spinal ganglia.
These preparations, which were very difficult to get, were then observed by Ron Oppenheim and me under the binocular scope and we found that the motility was exactly the same as in embryos which had only the dorsal gap. The dorsal gap reduces total motility. It was very clear that up to the point when the hatching movements begin, all motility is of the type described – self-generated. The only thing that was to be done after that – then came the anticlimax – I couldn’t go any further because I wasn’t an electrophysiologist and the people who worked with me: [Robert R.] Provine and Oppenheim, didn’t follow up. Provine did for a year or two but gave up. Oppenheim turned back to neuronal death and all that kind of stuff; didn’t develop an electrophysiological seminar. The only interesting thing I did with Oppenheim was to study hatching. That hadn’t been done by anybody since Réaumur, 1767 or ’85 [ed. note: actually 1751]. Nobody knew how a bird gets out of the egg.
That’s amazing.
Yes, particularly since there are so many _____(?) science departments. We did a very thorough job – spent a year and a half on that together, sitting there for many hours just looking at what happened. Worked that out. I think it’s a very good and very coherent story and it shows that the embryo switches fairly suddenly from the uncoordinated movements which I described before to a highly-complicated, highly-integrated set of movements that lead to hatching. There is no transition; it’s not so that this is gradually built up, but that comes triggered by hormonal or some other physiological conditions. Suddenly another type of movement comes into effect.
The last thing I want to say is that while we, quite correctly I think, stressed very strongly the lack of integration between the different parts of the body during activity phases. For instance, the eye can blink and the left leg can move and the two wings can be completely quiet – or one wing may just do the tiny movement in one joint and the leg may be very heavily activated in all its joints, so it is a complete lack of coordination. Then, one of our Ph.D. students, Ann Bekoff, discovered that at 7-1/2 days – that means at the moment when sensory input comes in – the synergistic and antagonistic muscles within the leg are already integrated. What we emphasized was the integration of different parts of the body, and what she showed is that does not mean that the entire program for antagonistic and synergistic movement in the leg is already prepared before sensory input takes over. So, I regret very much that this whole ten or twelve years of what I thought was original and important [work] has come into complete and total oblivion.
Well, that will change. The history of all the things you’ve talked about has had dormant periods, as you’ve referred to it, and I think this one may—
I’m sorry that I won’t live to see it revived.
You never know. I think at the end maybe it’s worth asking an obvious question, but one that’s nonetheless interesting, which is: looking back over what we’ve been talking about, what do you regard as the most important of these contributions?
Objectively, seen from the outside, it’s obviously the nerve growth factor.
Yes, but what do you think?
The most important thing, I think, was to have kept this whole area of trophic interactions alive. I mean, put it on the map, and provided the necessary tools to do the microsurgery that’s necessary to analyze these things. I would take credit for making it possible to operate on chick embryos the way people did for thirty years exclusively on amphibians. For the nervous system, certainly the chick embryo is more favorable because everybody knows, it has been shown over and over again, that the central nervous system and peripheral nervous system of the chick embryo is much more clear-cut, more highly-developed. You can be much more precise in asking questions and getting experimental designs than in amphibians. I would add that if people had started the retinal-tactile business on the chick embryo, an awful lot of confusion could have been avoided.
Thank you very much.
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