Talk:Paper - Development and transition of the testis, normal and abnormal 3

From Embryology

Sour. of An. & Phys, April 1588.

Vol. XXL. Asner Ce

cesar eet



SAV. F Huth, Lith? Edin™


F.R.CS., Hunterian Professor, Royal College of Surgeons, ingland. (PLaTE XVIT..)

(Continued from p. 77.)

Lecture III. Oviducts.

BEFORE proceeding with the transition of the testicles, the history of the oviducts, or, as they are usually called, the Miillerian ducts, may be briefly mentioned. Before referring to the development of these canals in rabbits’ embryos (the type which has been mainly used in these investigations) it is convenient to describe their appearances in certain pigs’ embryos, whose Wolffian bodies and ducts were exceedingly large, and in which the characters of the oviducts could be ascertained with some degree of certainty. These embryos, after hardening, were 1°8 c. long, and had fore and hind limbs of same length, but devoid of flexures or digits, and with the faintest trace of cartilage in their interior. The permanent kidneys had just developed, and the Wolffian bodies were exceedingly large, being 6 mm. long, and nearly at the period of their greatest development ; dorsalwards they were suspended in the pleuro-peritoneal sac by a broad mesentery; whilst ventralwards, along their middle third, the genital mass was united to them by a slightly constricted neck ; the genital mass was in the indifferent stage, and afforded no indication of its ultimate fate. The Wolffian ducts were exceedingly capacious, and lined throughout with a single layer of very short cubical epithelium. But, although the capacity of these ducts was so great, they caused no prominence upon the surface of the Wolffian body, except towards its hindermost end; there they gradually separated off and ran, in the midst of a cord of mesoblast, to empty into the urogenital sinus, 462 PROFESSOR C. B, LOCKWOOD.

The portions of the oviducts which had developed were A, their abdominal openings, and B,a short length of their epithelial lining. The abdominal opening (fig. 42) was situated towards the inner and ventral aspect of the Wolffian body and a short distance (twenty thin sections) from its foremost end ; it was lined with short columnar epithelium, continuous with that which clothed the Wolffian body and lined the rest of the pleuro-peritoneal sac; however, it is to be noticed that its cells were both larger and longer than those of the peritoneum. The inner and outer boundaries of the ostium were formed by two jutting processes, and the recess behind the outermost was continuous with the lumen of the oviduct. This continuity was effected very simply by the epithelial recesses becoming deeper, and extending further outwards, until, at last (fig. 43) it became a distinct canal, lying between the Wolffian duct and the peritoneal epithelium. Followed tailwards, this canal speedily lost its lumen (fig. 44), and ended in a solid column of cells, which was wedged in between the Wolffian duct and the peritoneal epithelium. The ostium of the oviduct is situated immediately in front of the foremost end of the genital mass (fig. 44), whilst its hinder impervious extremity reaches but a short distance tailwards. Thus, although the oviduct is still exceedingly rudimentary, it already affords evidence of its final disposition ; for, whilst its ostium is in front of the genital mass, 1ts canal courses round its outer margin to accompany, at last, the Wolffian duct. _

This specimen enables us to infer that, in some respects, the oviduct resembles the Wolffian duct. For instance, it is obvious that its foremost end develops sooner than its hinder part, and that the latter is at its first development like the Wolffian duct, in that it consists of a solid column of cells. However, the specimen affords no definite information as to the origin of the oviduet. Although the Wolffian and Miillerian ducts are so near to one another, yet the epithelium of the oviduct is so unlike that of the Wolffian duct, and so distinct from it, that it seems unlikely that it originated thence. On the other hand, there is no doubt whatever that the epithelium of the oviduct is continuous with the epithelium of the surface of the Wolffian body, and the weight of evidence seems in THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 463

favour of the view of Egli, Kolliker, and Janogik, that that is its source in the Mammalia. The researches of Balfour and Sedgwick, which were referred to in the first lecture, tend to show that in Aves the ostium of the oviduct is formed from the hinder groove of the pronephros. Therefore, before leaving this pig’s embryo, we might endeavour to ascertain whether it affords any information upon that point. Although I am unable to adduce any evidence of the actual existence of a pronephros in the pig, nevertheless, assuming that that organ had been present, it would be improbable for it to have helped in the formation of the oviduct, because the foremost part of that canal is some distance from the situation which the pronephros might be supposed to have occupied had it ever existed, being situated at least twenty sections beyond the foremost end of the mesonephros; this is borne out by longitudinal sections made from other members of the same litter.

The Wolffian body and its duct, and the rudiments of the oviduct, were so large and easy to observe in these pigs’ embryos that I regret to have been unable to obtain similar material for investigating the earlier stages. In rabbits’ embryos the early stage of the oviduct seems hard to observe; but the specimens in my possession bear out the statement made in the first lecture, to the effect that the structures which had been supposed to represent the pronephros entirely disappear, and therefore take no part in the formation of the oviduct. In other respects they countenance the view that the oviduct begins by an ingrowth of the epithelium of the urogenital ridge, and, finally, they fully bear out Kdélliker’s observations upon its later stages.

Genital Cord.

Although in the male the oviduct is functionless, and only represented by some interesting remains, nevertheless this circumstance has no particular influence upon the early stage of its development. This is exemplified by a human embryo which was mentioned in a previous lecture (Lect. II. p. 41), and which was {ths of an inch long, and estimated to have arrived at about the seventh week of intrauterine life. In this specimen the

1 Entwickelungsgeschichte, p. 977. 464 PROFESSOR C. B. LOCKWOOD,

genital mass was in the indifferent stage, and towards its upper end! there were several villous projections, the commencement, presumably, of the fimbriz of the oviduct, or, as later it is called, the Fallopian tube. The oviduct itself skirts round the outer margin of the genital mass, and after gradually approaching the Wolffian duct runs in company with that canal towards the lower end of the Wolffian body, where they together enter a thick mesoblastic cord, which is seen in a previous drawing (fix. 39, p. 61, Lect. IT). At this period, the seventh week, the cord which contains the Wolffian and Miillerian ducts is very short, and runs gradually inwards to unite with its fellow of the opposite side, and fuse with the mesoblast in which the urinary bladder is embedded. It is convenient to assign their names to these cords, and they should be called respectively the right and left genital cords and the common genital cord. ‘ As is well known, after the oviducts have entered the common genital cord they coalesce into a single canal, which ends in the urogenital sinus; the Wolffian ducts, on the other hand, remain apart, and open separately into the same space. In foetuses at full term it is usual to find the rudimentary oviduct, with a fimbriated end, lying in the digital fossa close to the globus major (v., fig. 45); this structure sometimes possesses a distinct canal. In the specimen which has been figured there are also two large spatulate and pedunculated bodies attached to the globus major; there is usually but one of these bodies, and their meaning seems still very obscure.*

Transition of the Ovary or Testis.

Method of Investigation.—Apparently the reproductive organs of the seven weeks’ human embryo which has just been referred to have, with reference to the other viscera, begun to occupy a lower position in the abdomen, or, in other words, the transition of the ovary or testis, whichever it may be about to become, has commenced.

1 So far specimens have been described as though the venter of the embryo was towards the ground. In this lecture the terms ordinarily adopted in human anatomy will be used, and the relations of structures spoken of as though the body was erect.

2 Wertheimer, art. ‘‘Testicule,” Dic. Encyclopédique des Sciences Médicales, p. 588. THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 465

The transition of the ovary and testicle has been mainly studied by dissection, and, perhaps, there is not much left to be ascertained by that method. For the earliest stages, however, it is desirable to use properly prepared series of histological sections, and since, as yet, this method has been but little used, I propose in that which follows to give the main facts learnt by its employment. By the paraffin method consecutive sections can be obtained in which the relations of the various organs to one another, and to the skeleton, can be studied without fear of disturbance. As the supply of reliable human embryos is necessarily limited, some of the earlier stages will, as a preliminary, be studied by means of rabbits’ embryos.

The transition of the reproductive gland has two stages; the first comprises alterations in its position within the abdominal cavity; the second its passage through the abdominal wall into the scrotum.

Before discussing these two phases, it is desirable to endeavour to determine upon what evidence movements of the ovary or testis may be judged to have taken place. It will be readily agreed that the relations of the gland to the skeleton, more particularly to the pelvis, are likely to yield the safest information upon this question. Therefore, for the present, I propose to consider the matter from this standpoint.

Earliest Relations of the Reproductive and Urinary Organs of the Rabbit to each other and to the Skeleton.

It is customary for authors to describe the position of the genital mass and Wolffian body with special reference to their relation to the kidney. This is calculated, I believe, to lead to erroneous conclusions, unless particular care is taken to observe their mutual relations to the skeleton. When, during the thirteenth day, the permanent kidneys of the rabbit appear, they are situated, as we have seen (Lecture II. p. 54, fig. 29, Pl. IL), behind the lower end of the Wolffian body and a little lower in the abdomen than the genital eminence. However, on the fourteenth day, the permanent kidneys have grown forwards (fig. 30, Pl. IT.) until they lie behind the middle third of the Wolffian body, and consequently opposite the genital 466 PROFESSOR CG. B. LOCKWOOD.

mass, This marks the point from which observers consider the transition of the testis or ovary begins. However, it is clearly wrong to speak of the testicle developing in front of the kidney, for the contrary 1s the case; and, as we have seen, the kidney develops after the Wolffian body and genital mass, and behind them. In these rabbits’ embryos it would be wrong, so far, to say that the genital mass and Wolffian body had begun to migrate, although, judging from their relations to the kidney, and assuming that the latter were immobile, it would be easy to imagine that movement had occurred. Another circumstance which might strengthen that impression is, that whilst the kidneys are developing, the lower end of the Wolffian body grows, as may be seen in the figure of the Wolffian body already described (fig. 39, Lect. II. p. 61), and tends towards the lower part of the abdomen. In consequence of this growth the Wolffian body appears lower in the abdomen, both as regards the kidney and as regards the skeleton. This point will be clearer as we proceed with the description of the transition in human embryos.

Thus, in the rabbit, the earliest changes in the mutual relations of the reproductive organs and kidneys are mainly due to growth and development in the organs themselves. The next step is to consider the early relations of the kidneys and reproductive organs to the cartilaginous skeleton.

Since the lower part of the vertebral column and pelvis are the portions of the skeleton with which the reproductive organs and kidneys are principally in relation, we will proceed with their early development. The Wolffian body and genital mass have attained considerable dimensions prior to the appearance of the cartilaginous vertebre. For instance, in the embryo of thirteen and a half days, whose Wolffian body and genital mass was described in the second lecture (Lect. IT. p. 46, fig. 37), the cartilaginous bodies of the vertebre could just be discerned. There was, however, no trace of the pelvic cartilages, and the hind limb consisted of nothing but mesoblast, blood-vessels, and nerves, together with a covering of epiblast. In this embryo the ureter had appeared, and ended in an irregular dilation a few sections nearer the tail than the hinder end of the Wolffian body.

The pelvic cartilages appear towards the end of the thirteenth THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 467

day close to the tail end of the Wolffian body. They originate. in a quantity of mesoblast which there is in that region, and an idea of the position of this mesoblast in the human embryo may be gathered from the drawing of a very early specimen given in the first lecture (vol. xxi. fig. 1, p. 637). The acetabular portion of the pelvis develops first, and the iliac cartilages extend from it behind the Wolffian body and towards the kidney. By the middle of the fourteenth day the iliac cartilage reaches well behind the Wolffian body; and the lower part of that organ is quite close to the lower part of the abdomen, and about opposite the head of the femur. Thus the Wolffian body of the rabbit acquires relations with the ventral surface of the pelvis, owing to the manner in which that part of the skeleton is developed, and not on account of any active movements which it (2.¢, the Wolffian body) may be supposed to have undergone. Moreover, after the growth of the iliac cartilages the position of these organs seems, by contrast, lower in the abdomen ; though, without doubt, the growth of the so-called urinary part of the Wolffian body conduces to this impression.

The influence of these processes of growth upon the apparent position of the genital mass may, perhaps, have been inferred. The first trace of the kidney develops behind the Wolffian body, opposite the lower end of the genital mass; the organ speedily grows, and by the fourteenth day reaches as far as the level of the upper end of the genital mass. At this stage I propose to leave this question, to be resumed by means of human embryos suitable for the investigation of the subsequent stages.

It is hard to ascertain the exact relation of the kidneys and reproductive organs to the spine, because no single longitudinal section divides sufficient of each to these organs to permit of a correct estimate. The most that can be safely affirmed is, that both kidney and genital mass lie opposite the lumbar spine, whilst the Wolffian body extends a little beyond above, and a great deal beyond below.

The acetabular portion of the pelvis develops almost opposite the lowest end of the Wolffian body, and therefore at some distance from either the kidney or genital mass; and although the iliac cartilage grows upwards behind the lower extremity of the Wolffian body, it has hardly, by the fourteenth day, reached 468 PROFESSOR C. B. LOCKWOOD.

as far as either the kidney or genital mass. If anything, it is nearer the lower extremity of the latter.

The foregoing account of the course of events in rabbits’ embryos has been given because those animals afford material of a fairly trustworthy character, and useful for checking that derived from human embryos. In endeavouring to ascertain how far that which they have taught is applicable to human embryos, the following points will be kept in view, namely, to ascertain the relations of the genital mass and Wolffian body to the kidney, and the relations of the genital mass, Wolffian bodies, and kidneys to the skeleton.

Earliest Relations of the Human Reproductive Glands and Urinary Organs to each other and to the Skeleton.

Although I have been unable to obtain human embryos suitable for showing each stage in the development of the permanent kidneys, yet there is little doubt but that those organs begin the same as in the rabbit. For instance,in a human embryo whose hind limbs had just budded, and whose development was almost equivalent to that of a rabbit’s embryo of the thirteenth day, the permanent kidneys lay behind the lower end of the Wolffian body and genital mass, and it was evident from their rudimentary structure that they had just appeared. Moreover, in sections through the lower end of the Wolffian body, the acetabular portion of the cartilaginous pelvis and the cartilaginous femur could be seen.

The observation that the human pelvis is developed in a solid mass of mesoblast opposite the lower end of the Wolffian body is borne out by other specimens, and they also show that the iliac cartilage grows upwards behind the end of that organ. In these respects the human embryo resembles the rabbit, and there can be no question but that its Wolffian body is likewise in relation with the venter of the pelvic cartilage, because of the manner in which the cartilage develops and grows, and not on account of movements which the excretory organ may have undergone.

Another human embryo a little more advanced, and which was estimated to have reached about the fifth week of intrauterine life, has been mentioned in which the kidney lay behind THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 469

the genital mass and Wolffian body, much in the same way as it did in the rabbit (fig. 31, Pl. IL). So that, up to this point, there seems to be no difference between rabbits and human embryos.

In a human embryo of the seventh week, which has been frequently mentioned, and whose reproductive organs have been figured (fig. 39, p. 61; also fig. 34, Pl. IT.), the various features are shown so clearly that it is proposed to describe them in greater detail.

The section which has been figured (fig. 46) is to the left of the vertebral column, and in its lower part divides the cartilaginous ilium and ischium, and a portion of the femur; in its upper part, amongst other things, the twelfth rib and diaphragm are in view. The histological structure of the kidney is very rudimentary, and that organ lies betwixt the last rib and the crest of the ilium, and almost equidistant from either of those landmarks, Only the lower end of the Wolffian body has been divided in this section, but, as in the case of the rabbit, 1t les upon the venter of the ilium, and reaches as low as the head of the femur.

In sections near the mesial plane the main part of the genital mass is just below the kidney, and on a level with the crest of the ilium (fig. 46), whilst its upper part, together with the sexual portion of the Wolffian body, extends along the convex margin of the kidney almost as far as the twelfth rib. It might easily be supposed that these appearances indicated that the genital mass had actually moved to a lower place in the abdomen, and this would be the more easily inferred if nothing but its relation to the kidney were taken into consideration. In a moment we shall see that its relations to the Wolffian body and to the skeleton have undergone no alterations which ought to be attributed to any process of locomotion, although it is probable that its relations to the kidney have become modified owing to the manner in which either organ develops. For instance, it seems possible that the part of the genital mass which is nearest the lower end of the kidney takes a greater share in the formation of the reproductive gland than the upper part. This seems to be so in rabbits of the latter part of the

thirteenth day, and also in rats of a similar degree of developVOL, XXIL (N.S. VOL, II.) 2H 470 PROFESSOR C. B. LOCKWOOD.

ment. In both of these the lower portion of the genital mass is much more bulky than the upper, and if the same holds good for human embryos, as it seems to do in the one we are discussing, it would naturally help to explain the relative positions of the organs to one another. Before mentioning the growth of the permanent kidneys, it is convenient to ascertain whether the Wolffian bodies have altered their relations to the newly formed cartilaginous skeleton; for it seems safe to assume that, if those organs have kept their position, the genital mass must have done the same.

I have already pointed out that the relation of the Wolffian body to the pelvis is determined by the manner in which that part of the skeleton develops behind its lower end. In the human embryo of the seventh week, which is being described, the acetabular portion of the pelvis occupies its original position at the lower end of the Wolffian body, although, as in the rabbit, the upward growth of the iliac cartilage makes the sexual organs look lower than they might otherwise do. Judging from its relations to the kidneys, the urinary portion of the Wolffian body seems decidedly lower in the abdomen. This, however, may be partially accounted for by the way in which the temporary and permanent urinary organs grow in relation to each other. Although the kidneys first appear behind the lower end of the Wolffian body, yet their growth seems to be upwards towards the head rather than downwards. Moreover, as we have seen, before the kidneys have attained much size or perfection, this so-called urinary portion of the Wolffian body increases, and tends towards the pelvis. These factors, taken together, seem almost sufficient to account for the relative positions which the kidneys and Wolffian bodies have assumed. ,

If we recall the early history of the Wolffian body, it is clear that its sexual portion still remains to be accounted for. This, in the specimen which is being described, is applied to the uppermost part of the genital mass (fig. 34, Pl. II. Lect. IT.), and lies outside the kidney, and above the level of the iliac crests. Therefore, it may be concluded that although the sexual portion of the mesonephros is undergoing changes, it has not altered its original position, but that various parts of the THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 471

skeleton and the kidneys themselves have developed and grown in its proximity.

Relation of the Mesonephros to the Suprarenal Bodies.

Should this line of argument be thought wanting in cogency, another circumstance may be mentioned which seems to show that neither the temporary kidneys nor their adjuncts, the genital masses, have altered their positions. In speaking of the sections through the inner part of the Wolffian body of this seven weeks’ embryo (Lect. IT. p. 71), it was said that “the foremost glomernli, although larger, are faintly stained, and their _tissues granular,—appearances which indicate that they have begun to degenerate and atrophy.” When this was written I felt uncertain whether this portion of the Wolffian body was continuous with the lower and inner part of the suprarenal body. It is so easy in histological specimens to fancy structures are continuous which merely overlap, that I refrained from making any statement upon the subject. However, after studying the “specimens over and over again during many months, I am of opinion that a portion of the mesonephros of this human embryo is in actual continuity with the suprarenal bodies. The part in question is that which is nearest the mesentery, and which, as has been repeatedly said, is mainly composed of glomeruli. _It reaches the lower and inner part of the suprarenal along the course of the ureter, and towards the upper part of the hilum of the kidney, but quite separate and. distinct from the substance of that organ. Not only am I unable to discover any line of demarcation between the glomerular part of the mesonephros and the suprarenal body, but those organs seem to merge gradually into one another; this is seen best by observing the glomeruli, which, whilst being quite distinct below, become fainter and more finely granular as they merge into the suprarenal (fig. 47). The main bulk of the latter is composed of small nucleated cells, arranged in the well-known radiate columns seen in the adult organ. Between these columns there is @ supporting stroma, which is directly continuous with that of the Wolffian body, which, it may be remembered, has already been depicted and described (Lect. II. Pl: I., fig. 24, and also p. 45). Towards the centre of the suprarenal body the radiate 472 PROFESSOR C. B. LOCKWOOD.

arrangement of its elements ceases, and instead are loculi of © cells more loosely aggregated, and of larger size and oval.


.. Suprarenal Body.


seams Kidney.

Wolffian B...


Fic. 47.—Continuity of Wolffian and Suprarenal Bodies in a Human Embryo of the seventh week.—(Electrotype from photograph of section.) !

The cortical portion of the suprarenal body of this seven weeks’ human embryo has an exceedingly strong likeness to the neighbouring genital mass in the following respects, namely, in the radiate arrangement of its cell elements, their size, shape, and staining, and also in the character of its stroma; although the last can only be considered a minor and perhaps unimportant point of resemblance. |

In due course I propose to discuss the position and relations of the sexual apparatus of another human embryo, which has been mentioned before, and which was estimated to have attained the tenth week of intrauterine life (Lect. II. fig. 40, p. 65). But, before commencing this topic, it is convenient to inquire whether it in any way confirms the statements which have just been made concerning the relation of the mesonephros to the suprarenal bodies. |

1 T am indebted to my friend Mr Cosens for the micro-photograph from which this electrotype was made. THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 473

In this embryo the kidneys lie opposite the lumbar spine, and their position is the same as in the younger specimen (fig. 40, Lect. II. p. 65). The suprarenal bodies are much larger than the kidneys, and occupy their usual position above those organs. Their lowest part reaches downwards a little beyond the hilum of the kidney. The testicle (for in this case the tunica albuginea and tubuli seminiferi have appeared (fig. 41, p. 66, Lect. II.)) and the Wolffian body, or, as it has almost become, the epididymis, lies just below the kidney and upon the venter of the iliac cartilage. In the section which has been figured there is not the slightest connection between the Wolffian body and the suprarenal body, but it may be remembered that in the younger embryo the junction between those organs was effected near the hilum of'the kidney by a process of glomerulus containing tissue which lay along the course of the ureter. Now, in the sections which divided that canal, there were in its neighbourhood structures which had all the appearances of those granular and altered glomeruli seen in the previous instance. Moreover, the lowest part of the suprarenal body extends so far into the hilum of the kidney, that although it is hard to tell whether in any particular section it is continuous with the peri-uretral glomerular tissue, nevertheless there is little doubt but that such is the case. But, in addition, the appearances of the lowest part of the suprarenal body are exceedingly significant. In every part of its circumference that organ has a very definite fibrous capsule, which delimits it from surrounding structures, except below, where its continuity is broken. In that region it is, I think, certain that some of the glomerular structures, such as lie along the course of the ureter, are imbedded in the cortex of the suprarenal body. In this older embryo the difficulty of arriving at a correct opinion upon this point is increased owing to the large size of the renal veins; but, nevertheless, the suprarenal body seems still connected with the Wolffian body, although the passage of the renal veins through the peri-uretral tissue renders their continuity harder to determine. I may add that there is not the slightest trace of any mixing of the renal tissues with those of the Wolffian body; on the contrary, the kidney has a definite capsule. Supposing these observations are correct, it 4:7 4, PROFESSOR C. B. LOCKWOOD.

is quite unnecessary to comment upon their importance. The recent observations of Mr Weldon! seem to show that there is in some types a close relationship between the early development of the suprarenal bodies and the glomeruli of the mesonephros. Also Janosik? has found that the suprarenals develop in connection with the foremost part of the urogenital ridge.

The human embryos of the seventh and tenth weeks, which have just been described, seem to indicate that the human suprarenal body has a developmental relation to the inner and upper part of the mesonephros. Doubtless the appearances of the glomeruli of that organ in the younger embryo indicate that an atrophic process has begun by which the mesonephros becomes eventually disconnected from the suprarenal; and it seems as if, in the older specimens, that disseverance was almost accomplished; and to this consummation the growth of the permanent kidneys and of their veins seems to have conduced.

The bearing of the foregoing upon the question whether the Wolffian body and genital mass of the seven weeks’ human embryo has descended in the abdomen or not can easily be inferred. Judging from their relations to the skeleton, it has already been decided that the sexual and urinary portions of its Wolffian body have undergone no actual alteration in position ; and now it may, with plausibility, be urged that the connection of its inner and upper part with the suprarenal body would render such movements exceedingly improbable. :

The human embryo of the tenth week is the earliest I have obtained in which the sex is not doubtful. It is hardly requisite to recapitulate the grounds upon which it has been decided that it is a male; the existence of the tunica albuginea testis, and unquestionable tubuli seminiferi are perhaps the most important. Therefore it is of especial interest to endeavour to ascertain whether, in this instance, the testicle and epididymis have undergone any active process of transition towards the lower part of the abdomen, or whether these organs have maintained the position which was determined for them by the development in their proximity of the kidneys and pelvis.

1 *¢Qn the Suprarenal Bodies of the Vertebrata,” W. F. R. Weldon, Quart. Jour. Mier, Sci., vol. xxv. p. 187, 1885.

2 ‘¢Bemerkungen tiber die Entwicklung der Nebenniere,” Archiv fir Micros, Anatomie, Band xxii., 1883, p. 738 é seq. THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 475

As regards the relation of the Wolffian body to the pelvis, some of the sections show that its urinary part is opposite the acetabular portion of the pelvis, and therefore has undergone no change since that part of the skeleton was developed in its vicinity. Also, it may be mentioned that the hypogastric arteries have attained considerable size, and project so far into the peritoneal sac that they almost touch the right and left genital strings, just after the latter have left the Wolffian bodies. Later in embryonic life it is probable that those vessels have an influence in determining the point at which, in the male, the sexual glands pass through the abdominal wall.

Although, therefore, the testicle and epididymis of this ten weeks’ embryo have maintained their original relations to the pelvis, yet, apparently, their relations to the kidneys have altered. This is due, as in previous instances, to (a) changes in the reproductive organs themselves, and (b) to changes in their surroundings, including the kidneys. It is convenient to begin with the last mentioned; and, in the first place, it seems improbable that the appearances can be due to any movements of the kidneys. In the seven weeks’ embryo those organs were situated opposite the lumbar spine, and now, at the tenth week, they still occupy the same position. In the interval, however, they have grown, and instead of being subordinate to the sexual organs they now surpass them. This circumstance has clearly an influence in determining the relation of the genital glands to the kidney.

The growth of the lumbar spine is also a factor which must be taken into consideration in speaking of the. influence which the growth of their surroundings may have upon the apparent position of the reproductive glands. Although, at the tenth week, the lumbar spine has grown a great deal, yet it has only kept pace with the growth of its contents and surroundings. The spinal medulla still extends the whole length of its canal (fig. 40, p. 65, Lect. II.), and the cauda equina and filum terminale are non-existent. In older embryos. the growth of the spinal column is so rapid that it far outstrips that of the spinal medulla, and, as is well known, leads to the formation of the last-named structures. Now, it is significant to observe that whilst the spinal column, especially of its lumbar part, is 476 PROFESSOR C. B. LOCKWOOD.

growing, the genital gland, either ovary or testis, separates from the kidney. During this separation the kidney remains immobile in front of the lumbar spine, and the sexual gland maintains its original relation to the pelvis, so that one important cause of the separation is not far to seek, and is,in my opinion, the growth of the lumbar spine.

We may now return to the human embryo of the tenth week, with a view of ascertaining whether any changes in the sexual gland and Wolffian body may have helped to bring them into position below the kidney.

It cannot be considered to have been proved that, in the human embryo, the lower part of the sexual eminence is actually converted into the testicle, but, nevertheless, that 1s possibly the case’; and I have already argued that the circumstance may partially account for the position of the genital mass in the embryo of the seventh week. In the present instance the genital mass has become the body of the testicle, and that organ is decidedly globose, and has ceased to extend around the outer convex border of the kidney, as it did at the earlier stage. Also, the sexual portion of the Wolffian body has become more closely applied to it, to form the epididymis. These circumstances, together with the incorporation of the upper and inner part of the Wolffian body in the adrenals and its partial atrophy, help to determine the position of the sexual glands below the kidneys.

The development of the ovary is not at present in question, but perhaps I may mention that the foregoing observations are, in all probability, applicable to eithersex. An exception to this statement must be made in respect to the shape of the ovary, for that organ does not become globular like the testicle, but retains to a certain degree the primitive elongated form of the sexual eminence.

In the human embryo of the twelfth week, and whose testicle has been figured (fig. 33, Pl. II. Lect. II.), that organ, as usual, lay in front of the ilium, and upon the brim of the pelvis; its lower part almost touched the hypogastric arteries, whilst its upper end is just in contact with the kidney. At this age the body of the testicle seems longer than the epididymis, and the latter has no upward prolongation. So far as concerns THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 477

its relation to the pelvis, the sexual gland is almost in the same position as 1t was in embryos of the seventh and tenth week ; but its mesentery is much longer than it was in them, and it is altogether more separate and distinct. Judging from the length of the spinal cord, the vertebral column has not grown very much, and has, so far, merely kept pace with the growth of the organs in its vicinity.

At the third month the position and connections of the testicle may be observed by ordinary dissection and with the naked eye. The sex of the embryo may also be ascertained in the same way by the shape of the sexual gland, and, more especially, by the direction of its long axis. In males the long axis of the testicle is vertical and its shape globular; whilst in females the long axis of the ovary is oblique, and the gland is decidedly spindle-shaped. It is hardly necessary to add that the external organs of generation are at this period the same in either sex, and therefore of no value for determining the sex.

Before proceeding, it may be advisable to enumerate the events which seem to participate in leaving the testicle or ovary upon the brim of the pelvis. I will endeavour to give them In their proper sequence. 1. Development of mesonephros. 2. Development of genital eminence. 8. Development and growth of kidney behind mesonephros and genital eminence. 4. Development and growth of pelvis behind lower end of mesonephros. 5. Alterations in upper part of mesonephros; its partial atrophy and probable incorporation in suprarenal capsule. 6. Growth of lumbar spine.


Fig. 42. Opening of oviduct of embryo pig into peritoneal cavity. Ov., oviduct ; W.B., Wolffian body ; Zng., lung; /., mesentery.

Fig. 43. Oviduct, where its lumen begins. Letters the same as fig. 42. J.P., inner process; W.G., Wolffian glomeruli.

Fig. 44. Oviduct near it hinder end. Letters the same as figs. 42 and 43. 0O.D., oviduct; G.I, genital mass. |

Fig. 45. A, B, and C, testicles of human fetuses ; P.V., plica vascularis ; O.D., remains of oviduct ; S.Hy., spatulate hydatid. Hy., hydatid of oviduet. 478 THE DEVELOPMENT AND TRANSITION OF THE TESTIS.

Fig. 46. Pelvic and lumbar regions of a human embryo of seventh week; #., ribs llth and 12th; Sup. &., Suprarenal body; K., kidney ; G.M., genital mass; W.B., Wolffian body ; J/., ilium ; Jsch., ischium ; Fem., femur ; Glut., gluteus maximus ; S¢., stomach.

Fig. 47. Electrotypes from micro-photo to show continuity of Wolffian body suprarenal (page 470).

Fig. 48. Human embryo of three months to show plica gubernatrix and position of testis; x3. 7, testicles; K., kidney; £, intestine ; P.V., plica vascularis; G.C., right and left genital cords; C.G.C, common genital cords; B., bladder; Gwub., plica gubernatrix and gubernaculum.

Fig. 49. Mesorchium and its folds (p. 60 ; woodcut).

Fig. 50. Ostium of processus vaginalis at fifth month. Tes., testicle; V.D., vas deferens; Gub., gubernaculum; P.G., plica gubernatrix ; P.V., processus vaginalis ; C., loose cellular tissue ; J/. Ves., iliac vessel ; Int. Ob. and Trans., internal oblique and transversalis muscles ; Hx. Ob., external oblique.

_ Fig. 51. Processus vaginalis in transverse section. Letters same as fig. 50 (woodcut).

Fig. 52. Unattached gubernaculum (woodcut).

Fig. 53. Gubernaculum of six months’ foetus. The peritoneum has been dissected from psoas and iliacus, and turned over the bladder in order to show the gubernaculum upon its outer surface ; 'P., peritoneum; Ant. S.Z., anterior superior spine of ilium; B. bladder; Hy. A., hypogastric arteries; 7., testicle; .G., gubernaculum ; Ps., psoas ; J1., iliacus ; Jné. Ob., internal oblique.

Fig. 54. Diagram constructed from sections and dissections of human foetuses at full time. To show peritoneal, scrotal, and perineal prolongations of the gubernaculum testis; C'@., cecum ; P. Vag., processus vaginalis; P., pubic bone ; Pl. Vas., plica vascularis ; Ep., epididymis; Tes., testicle; Pl. Gub., plica gubernatrix; G‘ub., gubernaculum ; Per., perineal fibres of the gubernaculum testis. |

Fig. 55. Infantile hernia to show the band of muscular fibres passing from epididymis to sac of hernia (woodcut).

Fig. 56. Processus vaginalis at eighth month of intra-uterine life to show the relations of the vas deferens and spermatic vessels to its posterior wall; S.V., spermatic vessels; V.D., vas deferens ; Ep., epididymis ; Tes., testicle; Gb., gubernaculum.

Fig. 57. Recurring branches of spermatic artery; S. A. and V,, spermatic artery and vein ; S., sigmoid flexure.