Meyer - Essays on the History of Embryology 10

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Meyer AW. 1932 - Essays on the History of Embryology: Part I | Part II | Part III | Part IV | Part V | Part VI | Part VII | Part VIII | Part IX | Part X | Part XI | Arthur Meyer | Historic Embryology Papers

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Arthur William Meyer (1873 – 1966)
Arthur William Meyer (1873 – 1966)

Essays on the History of Embryology X

By A. W. Meyer, M. D.

Stanford University

This is the ninth paper of a series of essays on this subject. Previous papers were printed in this journal as follows: Part I, in December California. and Western Medicine, page 447; Part II, in January number, page 40; Part III, in February number, page 105; Part IV, in March number, page 176; Part V, in April number, page 241; Part VI, in May number, page 341; Part VII, in June number, page 394; Part VIII, in July number, page 41; Part IX, in August number, page 111.

Bonnet

Bonnet, who called himself a pupil of Réaumur, experimented with aphidae and rediscovered the fact that parthogenetic - development occurs in them. He tells how he reared these insects to the eighth generation and how he made many experiments on polyps. He wrote a treatise on insects and made researches on the diverse uses of leaves in plants. Although Bonnet usually is regarded as a philosopher, he began his life work as an experimental naturalist. It is recorded that he remained such until his eyesight failed him through enthusiastic work with the microscope at the age of twenty-five. There can be little doubt that he never lost his interest in investigation or failed to recognize the great or even crucial value of a well—conceived experiment. He showed the liveliest interest in the experiments and observations of others and suggested experiments to them. In spite of his zealous defense of preformation, he always was ready to change his philosophical conceptions if they failed to account for observed facts. This is well illustrated by the modification of his ideas regarding emboitment. Bonnet’s objection toepigenesis apparently was that of those of the present day who reject the implication of spontaneous generation, for the epigenesists of his day did in fact assume that each organism arose anew from unorganized substances at the time of conception. Bonnet thought it seemed that Nature had jumped from the inorganic to the organic and felt that his successors might bridge the gap.


Bonnet’s experiments in embryology all bore on the question of generation and restitution of the individual. He was interested in, and experimentally tested, the regeneration of the heads of land snails, that of the limbs and tails of water salamanders, and also inquired into the same processes in crabs, worms, and polyps. He says that from this work he concluded that the assumption of the preéxistence of the germ offers the best explanation for the observed facts. In order to account for the many different portions of an organism that may be regenerated, Bonnet postulated that three forms of preformation are necessary for maintaining the integrity of the individual and one form for the perpetuation of the species. It was in connection with the latter that he accepted the idea of emboitment ad infinitum, at first, believing that each preformed individual possessed his specific, even if not his individual characteristics.

Experiments With Bees

Although they kept bees in glass hives, the older experimenters were unable to discover the manner of fertilization. Since they sometimes found that eggs which were not surrounded by “the whitish substance” failed to develop, they concluded that the absence of this substance was due to an oversight on the part of the males whose failure to add it to the eggs after they had been laid, was responsible for their failure to develop. Debraw, an English naturalist,‘ writing in 1776, declared that the eggs of bees only develop after the males deposit this whitish liquor found in appropriate vessels within their bodies, upon them. He referred to the ideas of Pliny and said that the “incomparable Réaumur” has “in a great measure removed the veil and brought their manner of generation nearly to proof.” He also quotes from the “celebrated Maraldi,” who after several years of work concluded that the eggs of the bee were fertilized after being laid. When speaking of Maraldi, Debraw wrote:


“This ingenious naturalist, by a nice examination of the structure of the drones, had, as well as Swammerdam, discovered some resemblances to the male organs of generation; and from thence conjectured, they were the males of the bee-insect; but he owns, with the rest, that he never could discover them in the act of copulation.


“Having stood the trials of so many prying eyes in every age, the bees, as has been observed by an ingenious author, had gained the character of an in violable chastity, till Réaumur blasted their reputation. He makes the queen no better than a Messalina; though he could see no more than what would raise a mere jealousy or generate suspicions.


“In order to be the better understood in the relation of my own experiments on the fecundation of bees, I here premise the outlines of the opinions adopted by the above-mentioned naturalists on that head. They assert, that the queen is the only female in the hive, and the mother of the next generation; that the drones are the males by which she is fecundated; and that the working bees, or bees that collect wax on the flowers, that knead it, and form from it the combs and cells which they afterwards fill with honey, are of neither sex.


“But of late Mr. Schirach, a German naturalist, has given us a very different view of the classes that constitute the republic of bees, in an ingenious publication in his own language, under the title of ‘The Natural History of the Queen of the Bees,’ which has been since translated into French; an account of which has been given in the Monthly Review, from which I beg leave to relate the author's doctrine with regard to the working-bees only; the quality and functions of the drones being points which do not appear to be yet settled by Mr. Schirach himself. He affirms, that all the common bees are females in disguise, in which the organs that distinguish the sex, and particularly the ovaria, are obliterated, or at least, through their excessive minuteness, have not yet been observed: that every one of those bees, in the earlier period of its existence, is capable of becoming a queen-bee, if the whole community should think proper to nurse it in a particular manner, and raise it to that rank. In short, that the queen-bee lays only two kinds of eggs, viz., those that are to produce the drones, and those from which the working—bees are to proceed.


“The trials made by Mr. Schirach seem to evince the truth of his conclusions in the most satisfactory manner, singular as they appear at first sight; and indeed in my own judgment, from the constant happy result of numerous experiments, which I began near two years before Mr. Schirach’s publication, and repeated every season since, I am enabled to pronounce on their reality.


“Chance, I own, befriended me in that discovery, whilst I was most anxiously endeavouring to ascertain the use of drones. It was in the spring of the year 1770, that I for the first, discovered what Maraldi had only conjectured, I mean the impregnation of the eggs by the males; and that I was made acquainted with the difference of size in the drones or males, observed by Maraldi in his ‘Observations Upon Bees,’ inserted in the History of the Royal Academy of Sciences for the year 1712, p. 333, in these words:


“We have of late found a great quantity of drones, much smaller than those we had formerly observed, and which do not exceed in size the common bees; so that it would not have been easy to distinguish them in that hive from the common bees, had not the quantity of them been very considerable. It might certainly have happened, that in those hives, where we have not been able to discover large drones, there were a great number of those little ones, which may have been_intermixed among common bees, when we were yet ignorant that any such small drones were existing.’


“Réaumur himself, p. 591, of his ‘Natural History of Insects,’ says, ‘We have likewise found drones that were no bigger than the common bees.’


“They have notwithstanding escaped the observation of Mr. Schirach, and of his friend Mr. Hattorf, member of an academy in Lusatia, who, in a memoir he presented in the year 1769, annihilates entirely the use of drones in a hive; and advances this singular opinion, that the queen-bee of a hive lays eggs which produces young ones, without having any communication with the drones. For what purpose should wise Nature then have furnished the drones with that large quantity of seminal liquor? To what use so large an apparatus of fecundating organs, so well described by Réaumur and Maraldi?


“But I beg leave to remark, that those gentlemen seem ‘to have drawn too hasty conclusion from their experiments, in rejecting the drones as bearing no share in the propagation of those insects. Their observations, that hives are peopled at a time of the year when there are no drones in being; is no way conclusive; as it is evident, that they had seen none but drones of a large size, their silence on the difference in the size of them justifying my remark. But to resume the narrative of my experiments: I had watched my glass-hives with indefatigable attention from the moment the bees, among which I had taken care to leave a large number of drones, were put into them, to the time of the queen laying her eggs, which generally happens the fourth or fifth day. I observed the first or second day (always before the third) from the time the eggs are placed in the cells, that a great number of bees, fastening themselves to one another, hung down in the form of a curtain, from the top to the bottom of the hive, in a similar manner they had done before at the time the queen deposited her eggs; an operation which (if we may conjecture at the instincts of insects) seems contrived to hide what is transacting: be that as it will, it answered the purpose of informing me that something was going forward. In fact, I presently after perceived several bees, the size of which, through this thick veil, (if I may so express myself) I could not rightly distinguish, inserting the posterior part of their bodies each into a cell, and sinking into it, where they continued but a little while. After they had retired, I saw plainly with the naked eye a small quantity of whitish liquor left in the angle of the basis of each cell, containing an egg: it was less liquid than honey, and had no sweet taste at all. Within a day after, I found this liquor absorbed into the embryo, which on the fourth day is converted into a small worm, to which the wor.king—bees bring a little honey for nourishment, during the first eight or ten days after its birth. After that time they cease to feed them; for they shut up the cells, where these embryos continue inclosed for ten days more, during which time they undergo various changes too tedious here to describe.

Fig. 6. Twin chicks, six days old, after Wolff.

“To evince the reality of this observation and to prove that the eggs are fecundated by the males, and that their presence is necessary at the time of breeding, I proceeded to the next experiments.


“They consisted in leaving in a hive the queen with only the common bees, without any drones, to see whether the eggs she laid would be prolific. I accordingly took a swarm, shook all the bees into a tub of water, and left them in it till they were quite senseless, which gave me an opportunity to distinguish the drones without any danger of being stung. After I had recovered the working-bees and their queen from the state they were in, by spreading them on brown paper in the sun, I replaced them in a glass hive, where they soon began to work as usual: the queen laid eggs, which I little suspected to be impregnated, as I thought I had separated all the drones or males, and therefore omitted watching the bees; but at the end of twenty days (the usual time of their hatching) I found to my surprize some of the eggs hatched into bees, others withered away, and several of them covered with honey. I immediately inferred that some of the males, having escaped my notice, had impregnated only part of the eggs; but, in order to convince myself of the truth of my supposition, I thought it necessary to take away all the brood-comb that was in the hive, in order to oblige the bees to provide a fresh quantity, being fully determined to watch narrowly their motions after new eggs should be deposited in the cells. This was done accordingly, and at last the mystery was unravelled. On the second day after the eggs were placed in the cells, I perceived the same operation which I have related in a former experiment; I mean, the bees hung down in the form of a curtain, while others thrust the posterior part of their body into the cells: I then introduced my hand into the hive, broke off a piece of the ‘comb containing two of those insects, and kept them for examination. I found in neither of them any sting, (a circumstance peculiar to drones only); and upon -dissection, by the help of a Dolland’s microscope, -discovered in them the four cylindrical bodies, which contain the glutinous liquor of a whitish colour, observed by Maraldi in the large drones.


“Having till then never observed any difference in ‘the size of drones, I immediately perused the memoirs on bees, published by Messrs. Maraldi and Réaumur, and found that they had remarked it frequently. I have inserted, in a preceding page, the substance of their observations on that head, as taken from their writings. The reason of that difference must, I doubt, be placed amongst other arcana of nature. I found myself, therefore, under a necessity, in my next experiments, to be more particular in destroying the males, even those which might be suspected to be such.


“I once more immersed all the same bees in water; .and. when they appeared-to be in a senseless state, I gently pressed every one of them between my fingers, in order to distinguish those armed with stings from those which had none, which last I might suspect to be males. Of these I found fifty-seven, exactly of the size of common bees, yielding a little whitish liquor on being pressed between the fingers. I killed every one, and replaced the swarm in a glass-hive, where they immediately applied again to the work of making cells; and on the fourth or fifth day, very early in the morning, I had the pleasure to see the queen-bee depositing her eggs in those cells; which she did by placing the posterior part of her body in each of them. I continued on the watch most part of the ensuing days, but could discover nothing of what I had seen before.


“The eggs, after the fourth day, instead of changing in the manner of caterpillars, were found in the same state they were in the first day, except that some of them were covered with honey. But a very singular event happened the next day about noon: all the bees left their own hive, and were seen attempting to get into a neighbouring common hive, on the stool of which I found their queen dead, having, no doubt, been slain in the engagement. The manner in which I account for this event is as follows: the great desire of perpetuating their species, which is most observable in these insects, and to which end the concurrence of the males seems so absolutely necessary, made them desert their own habitation, where no males were left, in order to fix their residence in a new one, in which, there being a good stock of males, they might the better accomplish their purpose. If this does not yet establish the reader’s faith of the necessity of the males bearing a share in the fecundation of the ova, the next experiment cannot, I presume, fail to convince him.


“I took the brood-comb which, as I observed before, had not been impregnated; I divided it into two parts; one I placed under a glass-bell, No. 1, with honey—comb for the bees’ food; I took care to leave a queen, but no drones, among the common bees I confined in it. The other piece of brood-comb I placed under another glass-bell, No. 2, with a few drones, a queen, and a number of common bees, proportioned to the size of the glass; the rest I disposed of as before. The result was, that in the glass, No. 1, no impregnation happened: the eggs remained in the same state they were in when put into the glass; and, upon giving the bees their liberty on the seventh day, they all flew away as was found to be the case in the former experiment: whereas, in the glass, No. 2, I saw, the very day after the bees had been put under it, the eggs; the bees did not leave their hive on receiving their liberty; and, in the course of twenty days, every egg underwent all the above mentioned necessary changes, and formed a pretty numerous young colony, in which I was not a little startled to find two queens.”


Gleichen, who also tried to mate ducks with roosters and rabbits, says that a marten unfortunately killed the two first after the cock had tread the duck, which, however, had laid eggs which were sterile. He stated that he never saw copulation between the rabbit and duck as reported by Réaumur and the writer of the letter to Noirmontier, which was cited by Buffon. Gleichen also repeated what he rightly called the ingenious experiments of Bengelin, reported in the Hamburger Magazine. The latter replaced the egg white in eggs of the hen, duck, and pigeon with that from those of other species. Gleichen, who repeated these experiments, found that the eggs always spoiled and he says he got nothing but an “insupportable stench for his trouble.” Since the same conditions always resulted whenever Gleichen exchanged the whites of eggs of the same species, he surmised that it was contact with the air which was responsible for the putrefaction and that an exchange of albumen in vacuum might succeed.


Gleichen, who was an animalculist, nevertheless opposed the preéxistence of germs, and said one could not see them in ova nor could one see the sperm in fertilized ova as one should be able to do if they penetrated the egg as some had held. He believed in crosses between the dog and hog, and the deer and the horse, and thought that children which resembled their mothers most were most likely to have maternal impressions. He also referred to the Gentlemen’: Magazine of the year 1757 in which the case of a hen egg is mentioned in which a toad was alleged to have been found, but thought the assertion of a Moravian soldier who claimed that he was pregnant, was probably the result of an idle brain.


Gleichen also mentioned the idea that the tail of the spermatozoon represents the precursor of the vertebral column and that hence only those animals which possess a tail in adult life should have tailed spermatozoa. He ‘says that this was his opinion and also that of Lieberkuhn and Hamburger, until he saw that spermatozoa of certain fishes are tailless.


It long had been a common opinion that the mammalian ovum passes from the ovary to the uterus through the tubes. This opinion probably was derived from observations on birds. Swammerdam also refers to the general belief that its passage gave rise to pleasurable sensations and sometimes caused swooning on the part of the mother. It also was firmly held that the tubal fimbria clasped the ovary to receive the ova as they were discharged, and it may be recalled that Leeuwenhoek protested against this idea.

Haighton

With pecuniary aid from William Hunter, Haighton undertook a carefully planned series of experiments in 1797 to determine whether ova really are discharged from the ovary, whether sperm must reach the ovary, and whether the presence of corpora lutea is a reliable sign of pregnancy. Haighton stated in this connection that “though some important facts are clearly ascertained, there are others still problematical. Physiologists are by no means agreed concerning the immediate cause of conception. All admit the necessity of sexual intercourse. They acknowledge, too, the necessity of some part of the female being affected by the direct contact of a fecundating fluid, but what the precise part is which must receivethe stimulus, has hitherto been involved in mystery and doubt. Nor are they more unanimous respecting the state or condition of the substance that passes from the ovaries; whether at the time of its expulsion it has a circumscribed vesicular character, or whether it has no‘determined figure. De Graaf and Malpighi, in the last century, and some respectable physiologists of the present day, adopt the first opinion; Haller and some others favour the last.”


From his first series of experiments on rabbits, Haighton concluded that the “corpora lutea furnished incontestable proof that impregnation either does exist, or has proceeded.” Haighton refers to Haller’s statement that he saw semen in the uterus of a sheep forty-five minutes after coitus, but he apparently was unconvinced and concluded from his experiments, that it is not necessary for semen to enter the uterus or tubes because if it were, ligation of the tubes should cause sterility. Strange as it may seem at first thought, Haighton concluded that his experiments showed that this is not the case. This was because he regarded the presence of corpora lutea as proof of the occurrence of impregnation in the ovary. Since corpora lutea formed on the side in which a tube had been ligated as well as on the unoperated side, his proof seemed incontestable to him. Haighton carefully compared the number of corpora on the two sides with the implantations on that side of the uterus and always found them to be the same on the unoperated side. He concluded that no uterine implantation had occurred on the side on which the tube had been ligated because the conceptuses were prevented from descending into the uterus and he hence regarded it as a law that “the ovaries can be affected by the stimulus of impregnation, without the contact of either palpable semen, or the aura seminalis.” He doubted the correctness of Nuck’s statement that he had produced an extra-uterine pregnancy in a rabbit by high ligation of the tubes, because it seemed to contradict the results of his own experiments, and concluded that the conceptions which he thought had occurred in the ovary on the side on which the tube had been ligated, did not continue their development because nature knew that it would be futile to have them do so.


Since Haighton could not find the ovum in the Graafian follicle although he found thirteen (blastocysts) in the tubes, one of which he actually had milked out, he concluded that “the semen first stimulates the vagina, os uteri, cavity of the uterus, or all of them. By sympathy the ovarian vesicles enlarge, project, and burst. By sympathy the tubes incline to the ovary and, having embraced them, convey the rudiments of the fetus into the uterus. By sympathy the uterus makes the necessary preparation for perfecting the formation and growth of the fetus; and, by sympa thy, the breasts furnish milk for its support after birth.”


Haighton had a very good idea of the size of the lumina of the tubes from passing mercury and air through them and gave criteria for distinguishing between hydatids or ovarian cysts, and mature Graafian follicles, but he probably mistook some immature follicles for cysts. As far as I am aware, he was the first to have established the fact that internal migration of the ovum does not occur in the rabbit, and although he could not discover an ovum in the Graafian follicle or between the ovary and the tubes, he nevertheless concluded that: “first, the ovum is formed in, and comes out of, the ovarium after conception. Second, it passes down the fallopian tube, and is some days in coming through it. Third, it is sometimes detained in the fallopian tube and prevented from getting into the uterus,” which he said it did on the fourth day in the rabbit.


(To Be Continued)


Historic Disclaimer - information about historic embryology pages 
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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms and interpretations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Meyer AW. 1932 - Essays on the History of Embryology: Part I | Part II | Part III | Part IV | Part V | Part VI | Part VII | Part VIII | Part IX | Part X | Part XI | Arthur Meyer | Historic Embryology Papers


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