Paper - A human embryo with head-process and commencing arch enteric canal

Embryology - 25 Apr 2024        Expand to Translate
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Thompson, P., and Brash, J. C. 1923. A human embryo with head-process and commencing arch enteric canal. J. Anat., 58, 1-20. PMID 17103992

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A Human Embryo with Head-Process and Commencing Archenteric Canal

By The Late Pnornsson PETER THOMPSON, M.D.,

University of Birmingham ,' Fellow of King’s College, Londan,

AND JAMES C. BRASH, M.A., M.D., B.Sc.,

Professor of Anatomy, University of Birmingham.

The clinical history of this embryo was detailed by the late Professor Thompson in his Ingleby Lecture before the University of Birmingham, in October, 1918. The first part of this paper, including the “General description of the Ovum,” he left in MS., and it represents all that he was able to complete for publication before his lamented death.—J. C. B.

Towards the end of the third or beginning of the fourth week, and immediately preceding the formation of the neural groove, the human embryo passes through a phase of development characterised by the presence of certain axial structures, viz. the primitive streak, a head -process canalised by a rudimentary archenteric canal, and the protochordal plate. Even to—day but few examples of this stage are on record, and Grosser, who has published an interesting account of a young human ovum which showed these structures with great clearness, claims that previous to l913—the date of his own pub1ication—a similar stage of development in man had not previously been recorded. In 1918 Ingalls published an account of a human embryo, somewhat less advanced in development, but strikingly like the preceding in all the essentials. A third example was recorded by Strahl in 1916, but up to the present the publication does not appear to have reached this country. Ingalls refers to it very briefly, and states that it shows a very similar stage of development, and adds that no data are given as to the age of the specimen.

The present paper is a further contribution to the subject, and, as far as can be ascertained, these four specimens comprise the material which illustrates a phase of development in the human embryo which falls somewhere between that represented by the ova of Fetzer, Von Herff and Beneke on the one hand, and that represented by the ova of Frassi and Eternod and Graf Spee’s Gle on the other. Estimating the age from the stage of development, Grosser gives 18 days, which is perhaps not far out. This archenteric stage, if such a term may be used for convenience, appears to be quite a transient one, and this may account for the small number of specimens which up to the present have been described.

The stage appears to correspond very closely with that which Wilson and Hill have described in their well-known work on monotreme development as the “post-gastrular stage.” They point out that this stage “includes the development, from the primitive knot, of the so-called ‘head-process’ together with various other phenomena associated with this, either causally or contemporaneously. This phase of development is deserving of special recognition,” they say, “as constituting a new era, for, with its onset, the process of ‘notogenesis’ is initiated, and the proper axis of the future embryo (Minot’s ‘primitive axis’) is laid down.” A full description of the axial structures in our embryo will be given at a later stage. In the first place it will be more convenient to set forth the details of the clinical history, which have been obtained with great care and are practically complete.

Clinical History

The ovum was removed from the uterus of a married lady by Mr Beckwith Whitehouse, F.R.C.S., on account of the serious condition of the patient’s health. It came into my hands on the following day, intact, and enclosed within a capsule of decidua. The following notes taken by Mr Whitehouse accompanied the specimen.

The patient, Mrs X, was seen in consultation on December 3rd, 1917. She was of a neurotic and highly sensitive disposition, and had suffered from nephroptosis, for which she had consulted a surgeon a short time previously with a view to an operation for its relief. Pregnancy, however, had supervened, and this fact, together with the knowledge of the pending operation, produced an exacerbation of the mental symptoms, and suicidal tendencies were exhibited. After full consultation it was decided to explore the cavity of the uterus and terminate pregnancy if such really existed.

The catamenial history had previously been quite regular—menstrual cycle 28 days. The last period began on October 25, 1917, and ended on November 1. No menstrual period occurred as expected on November 22. The husband, who had been away from home, returned on November 2, and coitus took place on the evening of November 6. Mr X left Birmingham on the morning of November 7, and no further coitus occurred. (The coitus previous to that of the evening of November 6 took place some time before October 23, the day on which the husband left on a business journey for South Wales, but how long before is uncertain. That no coitus took place between these two dates, i.e. October 23 and November 6, forces us to the conclusion that a previous cohabitation may be definitely rejected as a possible factor in the case.)

Three days later, i.e. on November 9, the patient complained of pains in the breast, and thought that she was pregnant.

On December 3, upon examination under an anaesthetic, the body of the uterus was found to be somewhat globular in shape and Very slightly enlarged. No softening of the cervix or other sign of pregnancy was present. However, taking into consideration the very slight increase in size of the organ, it was thought that a pregnancy might be present, and the uterine cavity was explored at 4.30 p.m.

The cervix was dilated by means of Hegar’s dilators, and a blunt curette was introduced into the cavity of the organ. Presupposing that the ovum was situated either at the fundus or on the posterior wall, curettage of this area was performed first. A small ovum was removed intact from the posterior wall and placed immediately in a 10 per cent. solution of formalin. No chorionic villi were observed, and the ovum appeared as a small disc-shaped vesicle about half an inch in its greatest diameter. A small quantity of decidual tissue was also removed by means of the curette from the anterior and lateral walls of the uterus. The cavity of the organ was then packed with gauze.

From a perusal of the medical history given above,_ and from data supplied to Mr Whitehouse and myself by the patient and her husband, both of whom realised the importance of exact statement, it seems certain that fertilisation must have taken place after and was presumably effected by coitus on the night November 6-7, 1917. It should be stated that the husband of Mrs X is a well-educated man occupying a professional position in the commercial life of Birmingham, and the history detailed above can, in my judgment, be im- plicitly relied upon.

The Age of the Specimen

Before entering upon a description of the embryo and its adnexa, some- thing must be said regarding that most diflicult problem, the age of the specimen. In our case we are in the fortunate position of knowing most of the essential facts, and yet the difficulties of arriving at a trustworthy conclusion within narrow limits are practically insuperable. Without a knowledge of such essential facts, the estimation of age is mere guesswork; with them we shall at least be able to arrive at an approximate estimate.

Moreover, from the standpoint of the history of the case, it is difficult to see how, under the circumstances, any additional or more reliable data could have been obtained, which would enable us to calculate the age with complete confidence. The really vital unknown factor is the day of the menstrual cycle on which the ovum was set free, and the absence of this knowledge is the barrier which hinders us in working out the problem with any degree of exactness.

The ovum was obtained thirty-nine days from the beginning of the last period, thirty-two days from the end of the period, eleven days from the omitted period, and twenty-seven (nearly) complete days after cohabitation. Assuming that an ovum was awaiting fertilisation, and allowing twenty-four hours for its occurrence, the absolute maximum time occupied by develop- ment was twenty-five or twenty-six days.

The fertilising coitus took place on the thirteenth day of the menstrual cycle, and sixteen days before the next expected but missed period. These days may well have been taken up by fertilisation, time consumed in travelling down the tube, the inhibition of menstruation, and the early stages of imbedding. In that case the ovum would reach the mucous membrane of the uterus towards the end of the menstrual cycle, that is to say, at a period well adapted to its nutritional requirements.

This leaves about twelve days from the time of the imbedding of the ovum to the termination of pregnancy by operation on December 3. Bryce and Teacher allowed seven days after implantation for the further growth and development of the young ovum described by them in 1908, and considering that our ovum is much more advanced in development, the additional five days seems a reasonable allowance.

But are the assumptions which we have had to make regarding ovulation and fertilisation justified in the present case‘? Certain considerations, which must next be advanced, seem to show that they are not, and that a period of six or seven days must be deducted if, on the ground of the degree of develop- ment, we assign our ovum to its appropriate place in the third week of the chronological tables of young ova compiled by Bryce and Teacher, Keibel and Mall, and Grosser. For, as everyone admits, it is necessary, in attempting to ascertain the age of a young ovum, to consider factors other than those avail- able in the obstetrical history of the case, and particularly the stage of develop- ment reached. Age and stage of development by no means always run parallel. For example, Keibel found in the pig differences which he regarded as equal to twenty-four to forty-eight hours’ growth at such an early date as the fourteenth day of pregnancy. Nevertheless, any marked discrepancy between the stage of development and the estimated age demands careful scrutiny.

Now the stage of development in the ovum under discussion approximates to that found in the ova of Grosser and Ingalls, both of which have been esti- mated to be eighteen or nineteen days old, and is undoubtedly earlier than that shown by the ova of Frassi, Eternod, Delporte and Graf Spee’s Gle, all of which have been placed at the end of the third week (nineteen to twenty- one days). True, amongst the six cases just noted, two only (Eternod’s and Delporte’s) have a clinical history comparable as regards fullness of detail with our specimen, but if, on the ground of the clinical history, it be main- tained that ours is about a week older than the stage of development suggests, then a place in the fourth week in the chronological tables mentioned above, in company with I-Iis’s Lg. and BB., would be incongruous.

Further, if the age of our ovum be estimated at eighteen to nineteen days on the ground of ‘anatomical findings, then fertilisation occurred on the twentieth to the twenty-second day of the previous menstrual month. Such a date would harmonise with the observations of Frankel on ovulation, which, based on one hundred and thirty-three laparotomies, go to show that ovulation occurs in the second half of the intermenstrual period, i.e. between the eleven to twenty-six days from the beginning of the last menstrual period, with an average of eighteen or nineteen days. In other words, ovulation would have occurred about one week after the fertilising coitus of November 6.

This would call for a sojourn of the spermatozoa in the Fallopian Tube of at least a week, a period during which it is reasonable to suppose they can

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Cite this page: Hill, M.A. (2024, April 25) Embryology Paper - A human embryo with head-process and commencing arch enteric canal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_A_human_embryo_with_head-process_and_commencing_arch_enteric_canal

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