COLUMBIA LIBRARIES OFFSITE 
 
 HEALTH SCIENCES STANDARD 
 
 HX64084760 
 QM41 6 .L81 Munterian lectures o 
 
 RECAP 
 
 
 LEWIS'S 
 
 ^ MEDICAL AND SGIEMTIFIG LIBRARY, 
 
 136 GOWER STREET, 
 
 XjOTSTX^OIST, -KKT-C 
 
 Buhscnptions from One Guinea pe)- Annum 
 
 ^'^fB^ ^ 
 
 r:i 
 
'V^ 
 
HUNTJliUAN LECTURES 
 
 ON THE 
 
 DEVELOPMENT AND TEANSITION OF THE TESTIS. 
 
HUNTEEIAN LECTURES 
 
 ON THE 
 
 DEVELOPMENT & TKANSITION 
 OE THE TESTIS 
 
 NOEMAL AND ABNORMAL 
 
 BY 
 CHAELES BAEEETT LOCKWOOD, E.E.C.S., 
 
 SURGEON TO THE GREAT NORTHERN CENTRAL HOSPITAL ; DEMONSTRATOR OP ANATOMY AND OPERATIVE 
 
 SURGERY IN ST BARTHOLOMEW'S HOSPITAL ; HITNTERIAN PROFESSOR OF ANATOMY, ROYAL 
 
 COLLEGE OF SURGEONS OF ENGLAND ; SECRETARY (in England) OF THE ANATOMICAL 
 
 SOCIETY OF GREAT BRITAIN AND IRELAND, &C. &C. 
 
 WILLIAMS & NO E GATE, 
 
 14 HENRIETTA STREET, COVENT GARDEN, LONDON 
 
 AND 20 SOUTH FREDERICK STREET, EDINBURGH. 
 
 1888. 
 
 Price Five ShiUingt>. 
 
K^itJJJIMJTyH 
 
 Ab-1iS-IOI3) c_ 
 
 ■12\ 
 
OO 
 
 a, 
 Ul 
 CO 
 
 PREFACE. 
 
 This book is a reprint of Lectures which have ah^eady 
 appeared in the Journal of Anatomy and Physiology, and 
 which, as Hunterian Professor, I had the honour to dehver 
 in March 1887 at the Eoyal College of Surgeons of England. 
 No alteration has been made in them, except that a few clerical 
 errors have been corrected. I have to tender my thanks to the 
 Editors of the Journal of Anatomy and Physiology for their 
 liberality in publishing and illustrating these investigations. 
 
 C. B. LOCKWOOD. 
 
 19 Upper Berkeley Street, 
 
 PoRTMAN Square, 
 
 July 1888. 
 
Digitized by tine Internet Arciiive 
 
 in 2010 witii funding from 
 Columbia University Libraries 
 
 http://www.archive.org/details/hunterianlecture01lock 
 
CONTENTS. 
 
 LECTURE I. 
 
 Metlioii of Investigation, 1 — Wolffian Body in Human Embryos, 1 — Wolffian 
 Duct of Chick, 5 — Epiblastic Origin of Wolffian Duct, 8 — Prolongation of 
 Body Cavity into Somite in Rabbit, 11 — Wolffian Tubules, 15 — The Prone- 
 phros, 21. 
 
 LECTURE II. 
 
 Glomeruli of Wolffian Body, 29 — Parenchyma of Wolffian Body, 36 — Develop- 
 ment of the Body of the Testis, 37 — Permanent Kidneys, 45 — Human Genital 
 Mass, 48 — Fusion of Wolffian Bodies — Synorchis, 49 — Mesorchium and 
 Mesovarium, 51 — Development of Tubuli Seminiferi, 53. 
 
 LECTURE III. 
 
 Oviducts, 67 — Genital Cord, 69— Transition of Ovary or Testis, 70 — Earliest 
 Relations of the Reproductive and Urinary Organs of the Rabbit to each other 
 and to the Skeleton, 71 — Earliest Relations of the Human Reproductive 
 Glands and Urinary Organs to each other and to the Skeleton. 74 — Relation 
 of the Mesonephros to the Suprarenal Bodies, 76 — The Development of the 
 Scrotum and Inguinal Canal, including the Ascending and Descending 
 Cremaster, 85 — Processus Vaginalis, 93 — The Transition of Sub-peritoneal Fat 
 and Lipoma of the Spermatic Cord, 96 — The Gubernaculum Testis, 96 — The 
 Cremaster, 107 — The Superior Attachments of the Gubernaculum, the 
 Mesorchium, and Plica Vascularis, 109 — Relation of the Vas Deferens and 
 Spermatic Vessels to Processus Vaginalis. The Recurrent Branches of the 
 Spermatic Artery, 116— The Closure of the Processus Vaginalis, 118. 
 
THE DEVELOPMENT AND TEANSITION OF THE 
 TESTIS, NOEMAL AND ABNOEMAL.^ 
 
 LECTURE I. 
 
 Method of Investigation. 
 
 Since our ultimate aim is to elucidate human anatomy and 
 pathology, it would seem an ideal plan to trace the development 
 of the testicles and their appendages in the human embryo ; but 
 unfortunately this is not entirely possible. A sufficient supply 
 of such material is hard to obtain, and that which is procurable 
 is seldom quite fresh and undamaged. The kindness of numerous 
 friends has, however, enabled me to investigate many interesting 
 points in human embryos, but not the very earliest, as these can 
 only be traced in the lower animals. Before attempting this 
 branch of the inquiry it may be best to glance for a moment at 
 the end which is achieved, and afterwards inquire how it has 
 been accomplished. The fact that the body of the testis and 
 the epididymis have different origins is too well known to call 
 for comment. The epididymis arises from a part of the Wolffian 
 body, the testis from a separate group of cells. The Wolffian 
 body has a prior claim upon our attention, for it has attained 
 a certain degree of perfection before the rudiments of the body 
 of the testis have appeared. 
 
 Wolffian Body in Human Embryos. 
 
 The smallest human embryo in which I have examined the 
 Wolffian body was seven thirty-seconds of an inch long ^ — about 
 the size of a small house fly. It is hard to estimate the age of 
 such an embryo as this, but it looks exactly like one which His 
 
 1 This paper consists of three lectures delivered to the Royal College of 
 Surgeons of England in February 1887. 
 
 2 I am indebted to Mr D'Arcy Power for this embryo, 
 
 A 
 
2 PROFESSOR C. B. LOCKWOOD. 
 
 considers to have been twenty-three days old.^ The most palpable 
 of its external characteristics were a considerable flexure of 
 the body and neck, an absence of limbs, and the presence of a 
 very obvious tail. Longitudinal sections show that the body is 
 divided into two compartments — a superior, containing the 
 heart ; and an inferior, containing the liver, lungs, alimentary 
 canal, and Wolffian bodies. 
 
 A glance at the accompanying figure (fig. 1) shows that, 
 owing to the absence of the diaphragm, there is no separate 
 pleural sac, but that the lungs lie in the upper part of a pleuro- 
 peritoneal cavity. The large size and the appearance of its 
 glomeruli render the Wolffian body a conspicuous object. 
 Occup3dng nearly all the back part of the pleuro-peritoneal 
 cavity, it reaches nearly as far forwards as the heart and peri- 
 cardium. Its front extremity is tapering and situated behind 
 the lungs, whilst the posterior is larger and extends towards the 
 hinder end of the pleuro-peritoneal cavity. 
 
 This brief description can hardly convey an adequate idea of 
 the enormous proportionate size of this part of the embryonic 
 excretory system. Perhaps it would not be incorrect to say 
 that at this period (the 23rd day) the length of the Wolffian 
 bodies is a third of that of the embryo, and that they constitute 
 a sixth part of its bulk. Another most interesting feature is 
 their extension towards the heart and pericardium, for it betrays 
 their close resemblance to the permanent kidneys of the lower 
 vertebrates, e.g., fishes. 
 
 Although this particular embryo serves admirably to display 
 the size and importance of the Wolffian body, yet it affords but 
 little information concerning its minute structure. In the 
 section drawn in fig. 1, the organ consists of a groundwork of 
 embryonic connective tissue, throughout which are numerous 
 round and oval spaces. These spaces are lined with minute 
 cubical cells, and a glomerulus protrudes from some part of the 
 wall into the interior. This arrangement holds good throughout 
 the whole length of the Wolffian body ; but it may be noticed 
 that anteriorly the glomeruli and the spaces which contain them 
 are smaller than elsewhere. Besides these glomeruli various 
 
 ^ His, Anatomic Menschlicher Embryonen, Leipzig, 1885, iii. ; Zur GescMchtc 
 der Organe, p. 238 ; Atlas, iii. Tafel x. fig. 7. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 3 
 
 tubules lined with epithelium may be made out in the other 
 sections, but, as these will soon be considered in detail, it is 
 unnecessary to do anything more than merely mention them. 
 Having now obtained a general idea of the Wolffian bodies of 
 
 Fig. l.—m., heart; P, lungs; L., liver; St., stomach; JV.B., Wolffian body; 
 C, tail ; T, tongue, x 25. 
 
 the human embryo, we may proceed to examine them in greater 
 detail. For this purpose transverse as well as longitudinal 
 sections are requisite, and a commencement may be made vnth 
 
4 PROFESSOR C. B. LOCKWOOD. 
 
 specimens which have been made from a human embryo a little 
 larger and more advanced than the last, and perhaps at about 
 the 26th day of intrauterine life.i The length of this specimen 
 was nearly half an inch, and the fore and hind limbs had just 
 begun to appear. The section which has been chosen (fig. 2) is 
 through about the middle of the embryo, and the organs divided 
 by it are the stomach, duodenum, liver, and Wolffian bodies. 
 The last named occupy no inconsiderable portion of the back of 
 the pleuro-peritoneal cavity, and their triangular shape is very 
 
 W.£). 
 
 Fig. 2. — St., stomach; i%. , mesogastrium ; fT.Z)., Wolffian duct; T, Wolffian 
 tubule; GZ., glomerulus; C.V., cardinal vein; ^0., Aorta; S.M., spinal 
 medulla, x 25. 
 
 unmistakable. The base of the triangle is towards the aorta 
 and vertebral column, and is continuous with the tissues which 
 surround those parts ; the sides are free, and look into the peri- 
 toneal cavity. The bulk of the Wolffian body consists of 
 embryonic connective tissue, and its surface is covered with a 
 layer of cells, which are thickest and most columnar round the 
 most prominent part of the organ. Beneath this covering and 
 near the apex of the triangle is a ring of concentrically arranged 
 cells, surrounding a small lumen, and this represents the 
 
 ^ This embryo was very like one depicted by His, Atlas, iii. Tafel x. fig. 9. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 5 
 
 Wolffian duct. On either side coiled tubules, the Wolffian 
 tubules, are apparent ; and on one side, the spectator's right, 
 the tubule seems to open into the duct. Moreover, in all 
 probability the tubule is connected with a large glomerulus, for 
 on either side these structures are prominent objects. Since 
 all the things which have been mentioned — duct, tubule, and 
 glomerulus — can be described better hereafter, a detailed account 
 of them will be deferred, and instead we will proceed to trace 
 their mode of origin. Before attempting to do this the large 
 veins in the back part of the Wolffian body may be noted ; they 
 are the cardinal veins, and are the channels by which the blood 
 from the primitive kidneys is returned to the heart. 
 
 It is clear that it is impossible to pursue this branch of the 
 inquiry upon human embryos, for it may have been noticed that 
 the organs in question had already, in the youngest embryos at 
 my disposal, attained a certain degree of perfection. The 
 important rSle which the Wolffian duct is destined to play is 
 betokened by the early age at which it appears. This point, 
 the origin of the Wolffian duct, is, as a preliminary, conveniently 
 studied in chicks, and although knowledge gleaned from them 
 is most valuable, yet perhaps it would be rash to assume its 
 applicability to the human subject without supplementing it 
 with information gathered from other sources. 
 
 A great many reasons might be adduced to show that in the 
 rabbit the process of development approximates very closely 
 that which has been observed in man. Moreover, that animal 
 has many advantages, which need not be mentioned, rendering- 
 it suitable for these investigations. Therefore I have availed 
 myself of the embryos of this animal, and whatever they have 
 taught will be mentioned in due course. 
 
 Wolffian Duct of Chick. 
 
 The phenomena which attend the development of the 
 Wolffian duct in the chick are difficult to observe, and author- 
 ities are not entirely agreed upon their interpretation.^ In 
 
 ^ Foster and Balfour {Elements of Embryology, 2nd ed., edited by Adam Sedg- 
 wick and Walter Heape, 1883, p. 94) say that the Wolffian duct may be seen 
 during the iirst half of the 2nd day. Mr Sedgwick ("The Early Develop- 
 ment of the Anterior Part of the Wolffian Duct and Body in the Chick, &c.," 
 
6 PROFESSOR C, B. LOCKWOOD. 
 
 order to obtain satisfactory information an embryo at about the 
 48th hour of incubation may be chosen.^ 
 
 In a transverse section through the middle of such an one it 
 is easy to recognise the various rudiments. It is unnecessary to 
 describe such well-known objects as the medullary canal and 
 the notochord, nor need particular stress be laid upon those 
 important membranes, the epiblast and hypoblast, for the 
 arrangement of the mesoblast, which lies between them, de- 
 mands all our attention (Plate I. fig. 1). Close to the medullary 
 canal the mesoblast is thicker than elsewhere, and forms the 
 mesoblastic somites or protovertebrse; beyond these it divides into 
 two layers, the somatopleure and splanchnopleure, separated by 
 an intervening space, the body cavity. It is important to note 
 that the somatopleure and splanchnopleure are united to the 
 somites by a neck of uncleft mesoblast, which is called the 
 intermediate cell mass, and which is said by many observers to 
 give origin to the Wolffian ducts. So far, the presence of the 
 latter in the section has not been mentioned, but nevertheless 
 they are quite clear and distinct. Upon one side, the spectator's 
 right, the Wolffian duct consists of a ring of cells surrounding a 
 small lumen. This ring is situated above the intermediate cell 
 mass,^ with which it has no connection, and lies in a bay made 
 by the somite on the inner side, and externally by the somato- 
 pleure, the epiblast completing it above (Plate I. fig. 1, W.D.). 
 On the opposite side, although the position of the collection of 
 cells, which afterwards forms the duct, is the same, it is question- 
 able whether it has any lumen, and, moreover, it is, in the clearest 
 way possible, united to the outer side of the adjacent somite. 
 Perhaps we may pause for a moment to comment upon these 
 facts. It is so clearly recognised that the Wolffian duct is at 
 first a solid column of cells, which afterwards becomes hollow, 
 that nothing more requires to be said upon that point, but its 
 
 Quarterly Journal of Micros. Sci., 1881, vol. xxi.) says that "the first trace of 
 the Wolffian duct is visible in an embryo with eight pro to vertebrae as a, slight 
 projection from the intermediate cell mass towards the epiblast in the region of 
 the 7th and 8th' pro to vertebrae." 
 
 ^ I am indebted to my friend Mr Ogle for the very beautiful specimens from 
 which these conclusions were drawn. 
 
 2 Until the later stages of development are treated, all relations ^ill be 
 described as though the embryo was placed with its ventral aspect towards the 
 ground. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 7 
 
 connection with the somite is another affair ; because, according 
 to some embryologists, the latter would be its normal origin, but 
 others are of opinion that it arises from the intermediate cell 
 mass. Under these circumstances it is interesting to note its 
 connections in this particular embryo. Anteriorly the duct is 
 united to the side of the somite (fig. 1), and, traced towards 
 the head, gradually ends upon it, disappearing by degrees ; 
 traced backwards, it first of all separates from the somite and 
 becomes distinct, but further back it joins the intermediate cell 
 mass, and terminates by mingling with it (Plate I. figs. 2 and 
 3, W.D.). My own experience is insufficient to permit me to 
 say whether there is a moment in the development of the 
 Wolffian duct at which it always conforms to this description, 
 but it does not seem unlikely, and the observation has the merit 
 of reconciling conflicting views. However this may be, an im- 
 portant principle underlies these matters of detail, and it is that 
 the Wolffian duct arises from mesoblast. As far as the chick is 
 concerned, this principle seems to be supported by ample histo- 
 logical proofs. Nevertheless, we must not hastily assume that 
 it is true, because, after a little consideration, it will be acknow- 
 ledged that there are a priori reasons with which the observa- 
 tion does not readily conform. For instance, in the case of 
 other glands it is possible to trace the origin of their epithelia 
 either to the epiblast or hypoblast, so that in the case of the 
 Wolffian duct of the chick there seems to be an exception to 
 what ought to be the rule. The difficulty would disappear if 
 credence could be given to the statements of Hensen and His, 
 that in the chick the Wolffian duct commences as a longitudinal 
 involution of epiblast.^ But the evidence to the contrary seems 
 so weighty, and the mesoblastic origin so clear, that the very 
 
 ^ Foster and Balfour, in their excellent manual, give a resumi of the views of 
 embryologists on this point (Foster and Balfour, Elements of Embryology, 1st ed., 
 p. 82, 1874). They say that Remak and Kolliker described the Wolffian duct as 
 taking origin from the mesoblast of the somatojileure. Dursy regarded it as being 
 derived from the pro to vertebra. Hensen, and for some time His, believed that 
 the duct began as a longitudinal involution of the epiblast external to the proto- 
 vertebrse. Subsequently His took the view that it was a product of the proto- 
 vertebrte. Waldeyer says the Wolffian duct originates from the intermediate cell 
 mass. But Waldeyer seems to think that the cells lining the duct are originally 
 derived from the epiblast. Quite recently Eomiti has described the Wolffian duct 
 as being an involution of the epithelium of the pleuro-peritoneal cavity. 
 
8 PROFESSOR C. B. LOCKWOOD. 
 
 strongest confirmatory evidence must be forthcoming before the 
 epiblastic parentage can be accepted. In truth, His, who at 
 one time advocated it, has greatly modified his opinion.-^ 
 
 Epiblastic Origin of Wolffian Duct. 
 
 The origin of the Wolffian duct is a problem so interesting to 
 the embryologist, and so important to the pathologist, that it 
 has not been allowed to slumber. Quite recently observations 
 have been published with the intention of proving its epiblastic 
 origin in the guinea pig and in the rabbit. So far as the former 
 is concerned, I am unable to adduce any evidence for or against, 
 but as regards the latter, specimens are at hand suitable for 
 investigating its truth. 
 
 A recent writer ^ has endeavoured to show that in the 
 rabbit's embryo certain thickenings of the epiblast separate 
 and become the Wolffian duct. Embryos of the 9th day 
 were used, and it may be stated that transverse sections 
 through the region of the duct closely resemble the trans- 
 verse sections of the chick (Plate I. figs. 1 and 2). They 
 are, however, much more advanced as regards the folding in 
 of the splanchnopleure, and in the development of the aortse 
 and body cavity. The epiblastic thickenings in question 
 are situated just above the intermediate cell mass and ex- 
 ternal to the somite (Plate I. fig. 5), and after examining 
 many embryos, I find that it is impossible to doubt that 
 they actually exist. Nothing could be clearer than the 
 diagrams which Flemming gives to show how the cells which 
 constitute these epiblastic enlargements become detached, and 
 form the Wolffian duct ; but, to my mind, the most important 
 evidence, that afforded by actual drawings, is inconclusive. The 
 matter is too important for summary dismissal, and perhaps the 
 actual specimens are inadequately represented by the figures. 
 
 ^ Graf Ferdinand Spee, in his paper ' 'Ueber directs Betheiligung des Ektoderms 
 an der Bildung der Urnierenanlage des Meerschweinchens," Arch. f. Anal, und 
 Phys., 1884, p. 89, gives a number of references to the literature of the subject. 
 The epiblastic thickenings which he delineates are singularly like some which 
 occur in both the rabbit and chick, and which will be referred to again presently. 
 
 2 "Die Ektoblastiche Anlage des urogenital Systems beim Kaninchen," Von V. 
 Flemming, Archivfilr Anatomie und Physiologie, 1886, p. 236, Tafel xi. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 9 
 
 Now, although in the rabbit the existence of these thickenings 
 is indubitable, it cannot be without significance to observe 
 that they are by no means confined to one position. The 
 cells of the epiblast seem to accumulate wherever the under- 
 lying mesoblast presents an inequality of its surface, and in 
 a specimen which had been taken from a nine days' rabbit 
 embryo (Plate I. fig. 5) there were distinct thickenings 
 at each side of the somites, and an additional one far away 
 from the side of the Wolffian duct in the bend which the 
 somatopleure makes as it turns backwards, and in fig. 9 
 there is an epiblastic thickening exactly over the dorsum of 
 the somite. It seems pertinent to ask whether we are to 
 assume that all of these thickenings are destined to become 
 Wolffian ducts. But however this may be, it seems quite 
 clear that in the rabbit embryos which I have examined 
 the Wolffian duct is in reality formed from a portion of the 
 cells of the intermediate cell mass.^ Those cells are at first 
 a solid column (Plate I. fig. 10, W.D.), but this in a little 
 while becomes hollowed out to form a real canal (Plate I. 
 figs. 5 and 9, W.D.). Of course this does not invalidate 
 the idea that the epiblastic enlargement which overlies the 
 intermediate cell mass may not participate in the production 
 of the duct, but assuming that was so, it seems natural to 
 infer that after producing the duct the swelling would alter. 
 It is true that the figures and diagrams which have been 
 mentioned show that this is supposed to be the course of 
 events, but nevertheless the specimens which I have exam- 
 ined cast doubt upon the matter, because in them both the 
 duct and epiblastic swelling coexist (Plate I. fig. 5, T.). Not 
 only may this be seen in rabbits, but in sections through 
 the hinder part of the forty-eight hours' chick, which has 
 been mentioned before (Plate I. figs. 3 and 4), it is clear 
 that the epiblast has thickenings analogous to those of the 
 rabbit's embryo, and, moreover, that the Wolffian duct arises 
 
 The specimens from which these observations were made are chromic acid 
 preparations stained with picrocarmine, and obtained in the summer of 1886. 
 Others have been prepared this summer (1887), which clearly bear out the views 
 which have been stated in this lecture. The last embryos were hardened in cor- 
 rosive sublimate and stained with borax carmine. 
 
10 PROFESSOR C. B. LOCKWOOD. 
 
 independently of them from the somite and intermediate cell 
 mass.i 
 
 It must be acknowledged that it is not an easy task to observe 
 the origin of the Wolffian duct in the rabbit's embryo, because 
 early embryos of that animal are exceedingly brittle and hard to 
 prepare. But Kolliker^ depicts the duct originating from the 
 intermediate cell mass, and, as may be seen, my own observa- 
 tions are confirmatory of the correctness of that view. Fig. 6 
 shows the intermediate cell mass of an early rabbit's embryo, 
 and it may be seen how strikingly it resembles the analogous 
 structure belonging to the chick ; and I have little doubt but 
 that it is the origin of the cell group from which the Wolffian 
 duct, and, as will be seen presently, the Wolffian tubules ori- 
 ginate. 
 
 Before proceeding further, a summary of the preceding con- 
 siderations may conduce to clearness, and they may be tabulated 
 as follows : — {a) In rabbit's embryos the epiblast has thickenings, 
 not only near the intermediate cell mass, but elsewhere; (6) 
 none of these thickenings are altered by the advent of the 
 Wolffian duct ; (c) the chick has similar thickenings, although 
 in it the Wolffian duct arises from the mesoblast. 
 
 Whatever may be the truth about the Wolffian duct, the 
 preceding observations tend to invalidate the idea that its origin 
 is from epiblast, but, without doubt, many will be reluctant to 
 admit their cogency. Such an admission is particularly hard 
 for the scientific pathologist, who is tempted to assume that the 
 epiblastic origin is true because it accords with a priori con- 
 ceptions. For instance, in the case of the testicle the assump- 
 tion that the Wolffian duct arises from epiblast has suggested a 
 plausible explanation of the origin of testicular carcinomatas, 
 but under the circumstances such an inference seems premature.^ 
 However clearly the epiblastic origin of the Wolffian duct is 
 
 ^ JanoSik, SitzungsbericMe der K. Akad. der Wissenschaften, Band xci. Heft 
 i. and ii., Wien, 1885, p. 113, repudiates Spee's observations, and says lie has 
 not seen epiblastic thickenings which he could consider the origin of the Wolffian 
 duct. JanoSik's monograph is clear, and gives a very good account of the 
 bibliography. 
 
 2 Kblliker, UntwicklungsgescMchte des Menschen und der Hoheren Thiere, 
 Leipzig, 1879, p. 277, figs. 197 and 198. 
 
 2 John Bland Sutton, An Introduction to General Pathology, 1886, p. 344. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 11 
 
 demonstrated, an obvious fallacy has to be guarded against. It 
 is superfluous to point out that nothing but a very simple con- 
 clusion ought logically to be drawn from that demonstration — 
 namely, that it may explain the origin of carcinomata from the 
 parts developed from the Wolffian duct and tubules. Presently 
 it will be seen what these are, but I may say at once that it is 
 doubtful whether any part of the body of the testicle ought to 
 be included. 
 
 Prolongation of Body Cavity into Soviite in Rabbit. 
 
 This seems a favourable place to mention an interesting 
 peculiarity of one of the specimens. It is usual in rabbits' 
 embryos, at the end of the 6th or beginning of the 7th day, 
 for the two divisions of the mesoblast to be continuous with one 
 another at the intermediate cell mass, so that there the walls of 
 the body cavity are quite unbroken. Moreover, the intermediate 
 cell mass intervenes between the cells which bound the body 
 cavity and those of the somite. The latter consists of a central 
 area of round cells, surrounded by a wall of others of a columnar 
 type (e.g., v. Plate I. fig. 5 or 6). The meaning of this cen- 
 tral area is not at a first glance particularly obvious, but the 
 following observation throws considerable light upon its mean- 
 ing. In a transverse section through a rabbit's embryo (fig. 7) 
 the walls of more columnar cells surrounding the central part of 
 the somite are particularly distinct and continuous with the 
 somatopleure and splanchnopleure. In consequence the central 
 area of the somite is a part of the general body cavity, to which 
 it is joined by a narrow passage which lies in the centre of the 
 isthmus, representing the intermediate cell mass.^ 
 
 Doubtless an observation founded upon the appearances of a 
 
 single embryo would not deserve to be recorded, if it was not in 
 
 accordance with our previous knowledge. As far as I am aware, 
 
 the body cavity is not known to be prolonged in mammalian 
 
 ^ George Renson, Archivfiir Mile. Anat., 1883, p. 600, "Eecherches sur le rein 
 cephalique et le corps de Wolff chez les Oiseaux et les Mammiferes. " In this 
 paper the author says he has seen this appearance in the chick, and calls the 
 canal the "canal de communication." He likewise quotes Kowalewsky (Die 
 Bildung der Urogenitalanlage hei Hiihnembryonen, Warschaw. , 1875, JaJires- 
 bericht, Hofmann und Schwalbe, 1875, p. 448), who first discovered this canal 
 in the chick. 
 
12 PROFESSOR C. B. LOCKWOOD. 
 
 embryos into the somites, but the appearances which have just 
 been described are very significant, and when we read what 
 Professor F. M. Balfour has written about elasmobranchs it must 
 be acknowledged that a summary dismissal of the subject would 
 be unmerited. This author points out that in some of those 
 fishes the body cavity extends into the somite, and proceeds : — 
 " The vertebral plate comes to consist of a series of rectangular 
 bodies, the mesoblastic somites, each composed of two layers, a 
 somatic and a splanchnic, between which is the cavity originally 
 
 continuous with the body cavity Between the vertebral 
 
 and lateral plates there is left a connecting isthmus, with a 
 narrow prolongation of the body cavity, which gives rise to the 
 segmental tubes, and to other parts of the excretory system."^ 
 This quotation shows that there is a strong resemblance between 
 the development of the rabbit and of this particular fish, and it 
 may help to explain the origin of the Wolfiian duct. It may 
 be remembered that the Wolffian duct, both in the rabbit and 
 the chick, has been said to begin as a column of cells which 
 afterwards became hollow. In seeking to explain the formation 
 of this canal, it is suggestive to find that in some animals it is 
 merely a shut-off portion of the body cavity, and further light is 
 thrown upon the question by observing that, even in the rabbit, 
 a part of the body cavity may once have occupied the place 
 where the Wolffian duct and tubules afterwards appear. Sup- 
 posing for a moment that we may assume that in rabbits, as in 
 some elasmobranchs, the lumen of the Wolffian duct is a shut- 
 off part of the body cavity, another objection remains to be dealt 
 with ; for if the assumption is admissible, why does the duct, in 
 most specimens, look like a solid column of cells ? We should 
 expect it to retain the lumen when once it has been acquired. 
 Although this is a weighty objection, it may lose some of its 
 force if we consider a thing which is often overlooked. It is the 
 custom to ascribe such preponderance to cells that the matrix in 
 which they lie is forgotten. Properly prepared embryos may be 
 seen to consist of cells embedded in a homogeneous matrix, and 
 I am inclined to think that in it are foreshadowed many changes 
 which occur in the arrangement of the cell elements. Therefore 
 
 1 Francis M. Balfour, A Treatise on Comparative Emlryology, 1885, vol. ii. 
 p. 48 et seq., also fig. 21. "~^ -■ ' 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 13 
 
 it is not impossible but that in the midst of cell groups ap- 
 parently solid many unsuspected matrix changes are hidden by 
 the cells themselves. However all this may be, it seems possible 
 that the force which hollows the Wolffian duct and tubules is 
 actually the same as that which makes the body cavity, and 
 that it is a part of the same process of cleavage.^ 
 
 After this I need not continue to discuss the actual origin of 
 the Wolffian duct, but will proceed with its subsequent history. 
 First of all, it is necessary to describe the way in which it alters 
 its position. It may be remembered that at the 9 th day, in 
 the rabbit's embryo, the duct lay beneath the epiblast, just 
 external to the somite and near the place where the somato- 
 pleure and splanchnopleure diverge to form the body cavity. 
 However, owing to changes in contiguous structures, it speedily 
 comes to lie beneath the cells which line the body cavity, and 
 even from the first a slight elevation denotes its situation 
 (Plate I. fig. 5). For reasons which will be clear after- 
 wards, this elevation may be called the urogenital ridge, and 
 the important events which occur in it will, for a time, mono- 
 polise all our attention. Perhaps it may be said in anticipation 
 that the development of the Wolffian tubules and of the body 
 of the testis are included in those events, but before beginning 
 this part of the subject it may be as well to say how the Wolffian 
 duct acquires its proximity to the body cavity. This is brought 
 about very simply in rabbits, for it seems to be accounted for 
 by an abrupt bending of the somatopleure backwards, and a 
 do%vnward shifting of the splanchnopleure (figs. 5 and 9). 
 This is hardly the place to discuss the cause of these changes, 
 but it may be explained that when the embryo first appears it 
 forms part of a blastodermic membrane, which is closely applied 
 to the uterine wall, with which the dorsal surface of the embryo 
 is in close contact. A little while after the advent of the 
 Wolffian tube, the axial part of the embryo shifts away from 
 the uterus, and consequently away from the plane of the peri- 
 pheral part of the blastoderm. Now, both the body and gut walls 
 of the embryo are continuous with the blastoderm, so that after 
 
 ^ KoUiker, he. cit., fig. 198, p. 279, portrays in the rabbit the Wolffian duct as 
 a fissure, such as might be expected had it been originally part of the body 
 cavity. 
 
14 PROFESSOK C. B. LOCKWOOD. 
 
 the embryo has moved they are necessarily bent backwards 
 towards the uterus. In the case of the body wall the bending 
 is very abrupt, and when its relation to the duct is noticed it is 
 easy to see how it makes the canal look more in relation with 
 the lining of the body cavity than it did previously (fig. 5). 
 
 Whilst the urogenital ridge has been appearing, other events 
 have happened. It may be remembered that originally the 
 Wolffian duct was represented by a solid column of cells (fig. 
 10) ; but these after a time arrange themselves in a ring 
 (Plate I. figs. 9 and 12), and a lumen appears in their midst. 
 When the canalisation is accomplished, the cells provide the 
 duct with a lining of columnar epithelium, which ultimately 
 becomes ciliated and surrounded by various coverings which 
 will be mentioned hereafter. During the progress of these 
 changes the duct has come to lie in the outer part of the 
 urogenital ridge close to the posterior recess of the body cavity 
 (fig. 12, W.D.), but another event of the greatest importance 
 has occurred, for the Wolffian tubules have appeared towards 
 its inner and ventral side. When this stage of development is 
 reached, the situation of the urogenital ridge is at the back of the 
 pleuroperitoneal cavity, and at either side of the newly formed 
 mesentery. Traced forwards, the ridge gradually dwindles, and 
 terminates near the heart, and backwards it may be followed as 
 far as the hinder part of the body cavity, but not quite to its 
 end. It is therefore evident that the urogenital ridge of the 
 rabbit has limits which correspond to those of the Wolffian body 
 of the human embryo (Plate I. fig. 1), and it clearly repre- 
 sents an early stage in the development of that structure. 
 
 The shifting of the splanchnopleure towards the ventral 
 aspect of the embryo, which is seen in embryos of the 9th day, 
 permits the urogenital ridge to protrude into a comparatively 
 wide body cavity (fig. 12), and there is nothing to interfere 
 with its growth, which goes on apace. By the 10th day it has 
 grown considerably, and the embryo has begun to assume its 
 more permanent characteristics. For instance, both the soma- 
 topleure and splanchnopleure have bent inwards towards the 
 ventral aspect, — the latter to form the gut and its mesentery, 
 the former the body wall. At this stage (fig. 12) a large part 
 of the urogenital ridge consists of mesoblast, in the midst of 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 15 
 
 which the "Wolffian duct and tubules are conspicuous. The 
 former lies in the back part of the ridge almost in contact with 
 the lining of the posterior recess of the body cavity, whilst the 
 tubules lie towards its inner side. It is important to note that 
 the epithelium which covers the ridge is slightly larger and a 
 little more columnar than elsewhere. It is called the germinal 
 epithelium. After these preliminaries, we have naturally arrived 
 at a point where the question of the origin of the Wolffian 
 tubules may be raised, and for a while that matter will occupy 
 our attention. 
 
 Wolffi^an Tubules. 
 
 Since it is unnecessary to comment upon the importance of 
 this part of the subject, I will proceed at once to discuss the 
 origin of the Wolffian tubules. Nearly all we know about this 
 question has been learnt from the chick, so that it will be best 
 to give a brief account of the phenomena seen in that animal, 
 and afterwards describe those which I have observed in rabbits 
 and in the human embryo. 
 
 What follows concerning the development of the Wolffian 
 tubules of the chick is in accordance with the statements made 
 in Foster and Balfour's well-known work on " Embryology."^ 
 Since the early development of the Wolffian duct of the 
 chick has already been briefly described, perhaps it is hardly 
 necessary to mention the changes by which it arrives beneath 
 the lining of the pleuroperitoneal cavity. The process is very 
 similar to that which has been seen in the rabbit, and the result 
 is that, finally, the duct lies beneath the peritoneal epithelium. 
 The tubules from their earliest appearance are very numerous, 
 and, in a sense, developed independently of the duct. In its 
 formation the latter does not monopolise all the intermediate 
 cell mass, but merely a part, and the remainder becomes con- 
 verted into the tubule. The process of conversion is not the 
 same everywhere, and, without doubt, the following quotation 
 will make the difference quite clear : — 
 
 " In front of about the sixteenth segment special parts of the 
 
 ^ Loc. ciL, •2nd ed., edited by Adam Sedgwick and Walter Heape, p. 190 ; also 
 Mr Sedgwick's very able paper upon the subject has been consulted {Quart. 
 Jour, of Micros. Sci., vol. xxi., 1881). 
 
16 PROFESSOR C. B. LOCKWOOD. 
 
 intermediate cell mass remain attached to the peritoneal epi- 
 thelium on this layer becoming differentiated, there being several 
 such parts to each segment. The parts of the intermediate cell 
 mass attached to the peritoneal epithelium become converted 
 into S-shaped cords, which soon unite with the Wolffian duct, 
 and constitute the primitive Wolffian tubules. Into the com- 
 mencement of each of these cords the lumen of the body cavity 
 is for a short distance prolonged, so that this part constitutes a 
 rudimentary peritoneal funnel, leading from the body cavity into 
 the lumen of the Wolffian tubule. 
 
 In the foremost Wolffian tubules, which never reach a very 
 complete development, the peritoneal funnels widen considerably. 
 The section of the tube adjoining the wide peritoneal funnel 
 becomes partially invaginated by the formation of a vascular 
 ingrowth known as a glomerulus, and this glomerulus soon 
 grows to such an extent as to project through the peritoneal 
 funnel, the neck of which it completely fills, into the body cavity. 
 There is thus formed a series of glomeruli belonging to the 
 anterior Wolffian tubuli projecting freely into the body cavity. 
 These glomeruli with their tubuli become, however, early 
 aborted." -^ 
 
 Before going any further it may be wise to pause and deal 
 with the questions which are raised by this quotation, and, 
 following its order the Wolffian tubules may be considered 
 first. 
 
 Theoretically speaking the simplest way in which the Wolffian 
 tubules could develop would be as outgrowths from the duct, 
 but the statement in the first sentence, that they arise independ- 
 ently, disposes of this idea, and a little further on it is said 
 that they proceed from the intermediate cell mass. In these 
 particulars the rabbit's embryo resembles the chick, for its 
 Wolffian tubules are not protrusions from the duct, but are 
 developed from a group of cells which is derived from the inter- 
 mediate cell mass. The meaning of this will be clearer if we 
 turn again to the rabbit's embryo at the beginning of the 9th 
 day. In such an one there is, in the position which the inter- 
 mediate cell mass would naturally occupy, a collection of cells 
 more or less surrounded by a delicate line of delimitation, and 
 ^ Foster and Balfour, 2nd ed., p. 191. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 17 
 
 lying between the external surface of the somite and the body 
 cavity (fig. 8). Before the end of the 9th day this group 
 alters, and the cells of it, which are near the epiblast, become 
 concentrically arranged to form the Wolffian duct, whilst the 
 others remain as a mass which is ultimately converted into 
 the tubules (fig. 9). At this stage the rudiments of the 
 tubules lie towards the ventral side of the duct, and in close 
 contact with the lining of the body cavity, but for the present 
 the question of their continuity with the latter may be deferred. 
 
 Before describing how the Wolffian tubules grow and acquire 
 a lumen, an interesting topic may be discussed. Apparently the 
 group of cells from which the duct and tubules are developed 
 extend without a breach from the posterior end of the body 
 cavity to within a short distance of the head. Now it is not 
 difficult to understand how a part of this column may become 
 converted into a continuous thing like the Wolffian duct, but it 
 is harder to appreciate the development of the tubules from the 
 remainder. Possibly comparative embryology may throw a little 
 light upon the point, and the researches of the late Professor 
 F. M. Balfour show that in the elasmobranchs " one segmental 
 tube (or Wolffian tube) makes its appearance for each somite, 
 commencing with that immediately behind the abdominal open- 
 ing of the segmental duct, the last tube being situated a few 
 segments behind the anus."^ Although this segmental arrange- 
 ment is not so obvious in the embryos of other types,^ yet it 
 doubtless foreshadows the principle which determines the group- 
 ing of the cells which become the Wolffian tubules. 
 
 I regret to have been unable to obtain satisfactory evidence 
 upon this point in rabbits' embryos ; but the appearances at 
 the 11th day^ were not uninteresting. At this time, owing 
 to the spiral form of the embryo, it is hardly possible to procure 
 good longitudinal sections, but occasionally a view of twelve 
 
 ^ Comparative Embryology, vol. ii. p. 692. 
 
 "Adam Sedgwick on "The Eai'ly Development of tlie Anterior Part of the 
 Wolffian Duct and Body in the Chick, &c.," Quart. Jour, of Mie. Sci., vol. xxi., 
 1881; also Studies from Morphological Laboratory in the University of Cambridge, 
 part ii., 1882, p. 13 et scq. 
 
 ^ Kolliker, loc. cit., fig. 293, p. 476, depicts a ten days' rabbit's embryo, which 
 corresponds to those which are here called eleven days'. The difference is 
 accounted for by obvious considerations, which need not be mentioned. 
 
 B 
 
18 PROFESSOR C. B. LOCKWOOD. 
 
 somites and their adjacent tubules was obtained. In a section 
 of this sort it was quite clear that, as a rule, two tubules 
 belonged to each somite ; but, here and there, it was hard to 
 say whether this number might not be exceeded ; at all events, 
 there were many more tubules than somites. Of course this 
 merely indicates the arrangement at that particular moment, 
 the 11th day. At earlier stages the conditions may resemble 
 the more primitive type, but this is perhaps unlikely in an 
 animal so high in the scale as the rabbit. 
 
 It has been said before that the Wolffian tubules are de- 
 veloped from a group of cells which lies in contact with the inner 
 and ventral side of the Wolffian duct, and we may now endeavour 
 to see how these acquire a lumen. In highly magnified longi- 
 tudinal sections (fig. 11), the elements which form the tubules 
 differ but little from those of the duct, and where both come 
 together there is no line of demarcation. Afterwards, by a 
 simple separation of the central cells, the lumen of the tubule 
 appears ; but at first the newly formed canal is without any 
 opening into the duct. A junction is obtained by a continua- 
 tion of the process which has just been described, for by a slight 
 severance of the cells of the duct- wall the lumen of the Wolffian 
 tubule becomes connected with the canal (Plate I. fig. 12). 
 
 Before leaving this part of the subject, perhaps I may 
 mention a circumstance which is shown in the drawing of the 
 longitudinal section. It may be noticed that although the 
 tubules are quite apart near the duct, nevertheless a little 
 further off they are united by a string of cells. Assuming that 
 this appearance is not due to any peculiarity of the sections, it 
 seems reasonable to suppose that it is the last trace of a 
 junction which, at one time, was much greater, perhaps com- 
 plete. However, the appearance is but temporary, and at later 
 stages there is no vestige of any union between the various 
 tubules. 
 
 If the preceding description of the development of the rabbit's 
 Wolffian tubules be compared with the account which Foster 
 and Balfour give of the same process in the chick it will be 
 manifest that a very important question still remains to be 
 discussed. It may be remembered that those authors write, 
 that in the chick the anterior tubules are, from their earliest 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 19 
 
 beginning, in continuity with the peritoneal epithelium ; as for 
 the other tubules, they say " in the posterior part of the 
 Wolffian body of the chick the intermediate cell mass becomes 
 very early detached from the peritoneal epithelium, and at a 
 considerably later period breaks into oval vesicles, which 
 elongate into Wolffian tubules.^ 
 
 Evidence has already been adduced to show that in the 
 rabbit the body cavity conforms with the conditions determined 
 in elasmobranchs (fig. 7). Perhaps it is unnecessary to repeat 
 how such an arrangement influences the relations of the 
 Wolffian duct and tubules of that animal to the peritoneal 
 epithelium and body cavity. Of course, if similar principles 
 of development obtain in the higher vertebrates as in the 
 elasmobranchs, we should expect to. find intimate relations 
 between the developing Wolffian tubules and the body cavity. 
 
 So far as concerns the chick nothing more need be said 
 upon this point, but as regards rabbits' and human embryos 
 no apology is called for before the matter is fully discussed. 
 
 Clearly the question now is to tell whether the Wolffian 
 tubules of the rabbit are, like the anterior tubules of the chick, 
 continuous with the peritoneal epithelium. In order to ascer- 
 tain this the nine days' rabbits' embryos, which have been men- 
 tioned before, are available. 2 It may be remembered that one 
 of these (fig. 8) showed a group of cells (the intermediate cell 
 mass) lying between the somite and the body cavity, and from 
 these the Wolffian duct and tubules originated. In a moment the 
 basis for this assumption will be more clearly indicated, but 
 our present object is to ascertain whether the cells are con- 
 tinuous with the peritoneal epithelium. It has been said 
 already that they are clearly delimited everywhere else except 
 near the peritoneal side, but, for the sake of simplicity, the 
 point in question was not referred to. However, it may now be 
 stated that, owing to the physical resemblances of the cells, 
 it is impossible to say where the cells of the tubule end or 
 where those of the peritoneum begin (figs. 8 and 9). In this 
 particular embryo the intermediate cell mass reaches as a 
 
 1 Foster and Balfour, 2nd ed., p. 192. 
 
 2 These embryos were a little more advanced tlian those which KoUiker 
 depicts, fig. 218, p. 298, and which are said to be of nine days and two hours. 
 
20 PROFESSOR C. B. LOCKWOOD. 
 
 distinct group of cells only a little way along either side of the 
 axis of the embryo ; but, doubtless, this need not be taken to 
 imply that the intermediate cell mass is of limited extent, but 
 merely that the cells which compose it may not differ from 
 their neighbours until about to undergo conversion into duct 
 and tubules. 
 
 It is a matter of some importance to follow this part of our 
 subject step by step. As the peculiarities of the tubules are 
 brought into view, fresh light will be thrown upon the question 
 of the origin of the Wolffian duct ; and this will further tend to 
 invalidate the idea of its epiblastic origin. An embryo belong- 
 ing to the same litter as the last is suitable for the purpose in 
 view, and, curiously enough, this second embryo seems in every 
 way more grown and developed than its fellows. In this case, 
 instead of finding an uniform mass of cells (intermediate cell 
 mass) between the somite and peritoneal epithelium, this 
 situation is occupied by the Wolffian duct and rudimentary 
 tubule (fig. 9). The duct is quite isolated from the surround- 
 ing structures, and no doubt as to its identity need be enter- 
 tained. The rudimentary tubules lie towards the ventral side 
 of the duct, and it is quite certain that where they are in contact 
 with the peritoneal epithelium no line of separation can be 
 discerned. Not only is this the case, but there is a distinct 
 resemblance between the cells of the tubules and the epithelium 
 which overlies them. In fact, observers are wont to say that 
 the epithelium grows in to form the tubule ; but, although 
 such an expression would affijrd an accurate idea of the appear- 
 ances in the rabbit, nevertheless it would convey a misleading 
 impression of the process. It would be more correct to say, 
 that as the cells of the intermediate cell mass differentiated into 
 the Wolffian tubules they assumed a greater resemblance to the 
 peritoneal epithelium. It must not be understood that the 
 preceding statements apply to all the tubules seen in this nine 
 days' embryo, for some of those near the tail end are certainly 
 not connected with the epithelium (fig. 10). Perhaps they are 
 developed independently in the intermediate cell mass ; and, if 
 this be so, it would show that there is a striking similarity 
 between the development of the rabbit and the chick, so far as 
 their Wolffian tubules are concerned. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 21 
 
 It is important to tell how many of the tubules are connected 
 with the epithelium, but the endeavour has not yielded satisfac- 
 tory information. Proceeding, therefore, with other questions, 
 we notice that in embryos of the 11th day the junction between 
 the' front tubules and the peritoneal epithelium is very clearly 
 marked, and on the 13th day not only is this the case, but 
 fresh peculiarities have appeared. Before these are mentioned 
 it may be as well to comment upon the significance of some of 
 the preceding statements, and in doing so advance another step. 
 First of all, a very simple inference may be drawn from the 
 fact that in the second embryo the situation of the intermediate 
 cell mass is occupied by the Wolffian duct and rudimentary 
 tubules, viz., that the mass has actually separated into those 
 two structures ; or the matter might be put differently by 
 saying that the cells of the intermediate cell mass nearest the 
 epiblast simply became the duct, and that the others remained 
 as the tubule. Since, therefore, the Wolffian tubules of the 
 rabbit are continuous with the peritoneal epithelium, we may 
 now proceed to ascertain whether their lumens communicate 
 with the body cavity. 
 
 The Pronephros. 
 
 The comparative embryology of the vertebrate excretory 
 system is so abstruse that it would be out of place, under such 
 circumstances as these, to attempt its explanation. Those who 
 have paid attention to the subject know that the Wolffian body, 
 which so far is the only organ that has been mentioned, repre- 
 sents but a portion of the entire system. Sedgwick ^ in his able 
 monograph, says, " The most peculiar feature of the excretory 
 system of the vertebrate is the presence of three more or less 
 distinct parts — the pronephros, the mesonephros, and the meta- 
 nephros, or kidney proper." The mesonephros is the organ 
 which in these pages has been described under the name of the 
 Wolffian body, but nothing whatever has been said concerning ' 
 the pronephros. Obviously, before it is possible to say whether 
 
 ^ "On the Early Development of tlie Anterior Part of the Wolffian Duct and 
 Body of the Chick," &c.. Quart. Jour. Micros. Sci., vol. xxi., 1881; also Gegeu- 
 haur, Elements of Comparative Anatomy, translated, &c. , by Bell and Lankester, 
 London, 1878, p. 603. 
 
22 PROFESSOR C. B. LOCKWOOD. 
 
 this organ is represented in the rabbit, it is necessary to ascer- 
 tain by what characteristics it may be recognised, and for this 
 purpose Sedgwick may be quoted. First of all, it is stated that 
 " the pronephros when present always develops in continuity 
 with the anterior end of the segmental duct." The initial step 
 in the inquiry is therefore exceedingly simple, for, since the 
 Wolffian and segmental ducts may be considered the same, all 
 that is requisite is to examine the front end of that canal. 
 Next, it is said^ that — 
 
 " In the Amphibian the segmental duct arises as a groove of the 
 parietal peritoneum, just ventral to the place where the body cavity 
 is connected with the cavities of the muscle plates. This groove, 
 which arises first of all anteriorly just behind the branchial region, is 
 continued for a certain distance backward. It soon, however, becomes 
 constricted into a canal lying between the ectoderm (epiblast) and 
 parietal peritoneum. This constriction has been described as taking 
 place in the following manner : — It first appears in the middle region 
 of the groove, giving rise to a canal opening into the body cavity in 
 front and behind. It then is continued backwards until the groove 
 is completely converted into a canal behind, which soon acquires an 
 opening into the cloaca. Anteriorly the wide opening meanwhile is 
 divided up into two (urodela), three (anura), or four openings 
 (csecilia), according to the species. 
 
 " The canal immediately behind the last of these openings becomes 
 coiled, and placed on the same level, but ventral to the openings. 
 The part of the body cavity into which the openings of the segmental 
 duct pass widens out, a vascular projection — the glomerulus — from 
 the dorsal inner wall is formed, extending uninterruptedly from 
 opposite the anterior opening of the segmental duct to as far back as 
 the posterior. The dilated section of the body cavity in which the 
 glomerulus lies, and into which the openings of the segmental duct 
 opens, is partially separated from the rest of the body cavity. The 
 whole structure, including openings of duct, ventral coiled part of 
 duct, glomerulus, and dilated part of body cavity, is known as the 
 pronephros." ^ 
 
 Although the question only refers to Amphibians, the matter 
 
 has been carried a step further by the discovery of similar organs 
 
 ^ Gegenbaur {Elements of Comparative Anatomy, translated by J. Bell, 1878, 
 pp. 601, &c.) calls the duct wliicli belongs to the pronephros and mesonephros 
 the " arichinephric duct," and says that it originates from the mesoderm. 
 
 2 Upon this subject Balfour's monograph "On the Nature of the Organ in 
 Adult Teleosteans and Ganoids, which is usually regarded as the Head Kidney or 
 Pronephros, " Studies from. Morphological Laboratory in the University of Cambridge, 
 1882, p. 69, may be consulted ; also Messrs Balfour and Sedgwick's joint mono- 
 graph "On the Existence of a Head Kidney in the Embryo Chick," &c., Quart. 
 Jour. Micros. Sci., vol. xix., 1878. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 23 
 
 in the chick and other birds.^ Not only are the above-men- 
 tioned openings represented in that animal, but glomerular 
 structures protrude from them into the body cavity. However, 
 in rabbits and human embryos similar protrusions cannot be 
 found,^ although passages leading from the body cavity into the 
 Wolffian duct or tubules undoubtedly exist, and attention may 
 now be given to them. 
 
 It may be remembered that the development of the "Wolffian 
 bodies has been traced step by step until the organs were found 
 to consist of a duct, with rudimentary tubules towards their 
 inner sides. These structures, together with their surrounding 
 mesoblastic tissue, lay in a fairly prominent ridge (the uro- 
 genital ridge), situated at either side of the mesentery. More- 
 over, it was said that the urogenital ridge extended towards the 
 front of the body cavity, dwindling gradually, and ended behind 
 the lungs, and close to the sinus venosus. The great blood- 
 vessel of the Wolffian body (the cardinal vein) courses along 
 immediately behind the duct, for which it is a convenient land- 
 mark. 
 
 After this recapitulation the peculiarities of the front part of 
 the Wolffian body and duct may be followed with greater ease, 
 and first of all its termination may be discussed. It has been 
 found that embryo rabbits at the beginning of the 13th day 
 afford the most satisfactory information. To give an idea of the 
 development of such specimens they may be compared to chicks 
 at the end of the 3rd day of incubation, and the comparison is 
 borne out by the fact that the limbs of the rabbit have budded, 
 and its crystalline lens has appeared.^ However, it is necessary 
 to say that a mere statement of the number of days which may 
 have elapsed since impregnation seldom conveys a correct 
 notion of the degree of development any particular embryo 
 may have attained ; so that it may be asserted that is not pos- 
 sible to foretell what embryos will be like any particular time 
 after impregnation, nor can any one be sure that the individual 
 
 ^ JanoSik says he has seen the fore kidney in the chick, quail, pigeon, and 
 duck, ibid., p. 125. 
 
 2 JanoSik is of the same opinion as regards rabbits, loc. cit., p. 128. 
 
 ^ Foster and Balfour, 2nd ed., chap. vi. fig. 65, p. 188, give a diagram of a 
 3rd day's chick, which is comparable to the rabbit's embryo at the beginning of 
 the 13th day. 
 
24 PKOFESSOR C. B. LOCKWOOD. 
 
 members of a litter will be alike ; indeed, in the earlier stages 
 they vary exceedingly. If now we return to the rabbit's embryo 
 at the beginning of the 13th day, and investigate the most 
 anterior portion of its Wolffian duct, it is found that a short 
 length of it is detached and separate from the main canal.^ 
 This isolated front part consists of a solid column of cells 
 (fig. 13) wedged in between the cardinal vein and the peritoneal 
 epithelium, but before it ends posteriorly it has a lumen which 
 is probably connected by two apertures — nephrostomata — with 
 the body cavity (fig. 14). The histology of these communica- 
 tions is quite simple, for, where they are found, the outer side 
 of the duct seems simply blended with the neighbouring epi- 
 thelium, and through the midst of this connection there is 
 apparently a narrow channel.^ A very little way further back 
 than this curious organ the Wolffian duct recommences, and, 
 almost directly after its new beginning, it is united to the body 
 cavity by a process of cells almost the same as those belonging 
 to the detached portion of the duct (fig. 15). But, in addition, 
 the urogenital ridge in this region has a peculiarity, for its 
 most convex part is slightly grooved (fig. 16). Some thickened 
 epithelium which lines the groove reaches towards the Wolffian 
 duct. The succeeding sections show that this epithelial thick- 
 ening is continuous with a somewhat tortuous Wolffian tubule, 
 which opens in the usual way into the duct.^ From this point 
 the Wolffian duct and tubules, traced backwards, conform to the 
 description which has been given in previous pages. 
 
 Assuming the correctness of the foregoing account, it is clear 
 that at the beginning of the 13th day the front part of the 
 rabbit's Wolffian body resembles in some respects the organ 
 which, in the chick, has been called the pronephros. It is true 
 that there is a difference, for the presence of glomeruli has not 
 been determined. An observer * has stated that in twelve days' 
 
 ^ Sedgwick {On the Early Development of the Anterior Part of the Wolffian Duct 
 and Body in the Chick, p. 16) mentions similar appearances in chicks. 
 
 2 Upon this point Janosik and Eensen may he consulted. They describe very 
 similar appearances. Janosik says that he has seen four nephrostomata. The 
 specimen I have described had but three. 
 
 3 I have never seen the Wolffian tubules of the rabbit open into the body 
 cavity vrith the exception of the tubules which have been described, and which 
 seem to possess nephrostomata. 
 
 ^ Rensen, loc. cit., p. 607. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 2d 
 
 rabbits he has seen " from place to place the pleuroperitoneal 
 epithelium adjacent to this canal (Wolffian) present traces of a 
 cellular proliferation, in which can be seen the last vestiges of 
 external glomeruli." Now, in the chick, the external glomeruli 
 are very distinct structures, and not only have other observers ^ 
 failed to discover their analogues in rabbits, but, judging from 
 the specimens I have examined, the vestiges mentioned in the 
 quotation are exceedingly dubious. Nevertheless, the absence 
 of an external glomerulus is not an insuperable objection to 
 the hypothesis that rudiments of a head kidney or pronephros 
 exist in the rabbit, because, as Sedgwick seems to point out,^ 
 they are not an essential feature of the organ. Before taking 
 leave of this interesting question, the nephrostomata demand 
 further notice. It is possible that those apertures represent 
 Wolffian tubules in a less complete state of development than 
 elsewhere, but if this is the case they must have become con- 
 siderably modified.^ For instance, they are joined to the outer 
 side of the duct, and not to its inner and ventral side like the 
 true tubules ; secondly, a section sometimes shows a nephro- 
 stoma opening by itself into the duct, whilst there may be, in 
 the same section, a tubule to the inner side (fig. 15); finally, 
 the Wolffian tubules blend with the epithelium of the body 
 cavity at the most convex part of the urogenital ridge, and not 
 at its outer side, like the nephrostomata. Concerning the 
 groove that has been mentioned (fig. 16), it would be improper 
 to say more than that it has a certain resemblance to the grooves 
 seen at the fore end of the chick's excretory apparatus, and which 
 are considered to be an important part of its pronephros. 
 
 The foregoing observations cannot be considered complete 
 until it has been ascertained whether they are applicable to the 
 human embryo. It may have been inferred, from what has been 
 said, and from the figures which have been given, that the 
 human embryo has a Wolffian body which closely resembles that 
 of the rabbit. A glance shows that in either case its configura- 
 tion is the same, and no difference can be detected in its con- 
 
 ^ JanoSik, loc, cit. 
 
 ^ Sedgwick, Early Development of the Anterior Part of the Wolffian Duct and 
 Body in the Chick, &c. , p. 25 et seq. 
 
 ^ If we may judge from Mr Sedgwick's [loc. cit., figs. 13 and 14) figures the 
 nephrostomata of the chick and rabbit are not dissimilar. 
 
26 PROFESSOR C. B. LOCKWOOD. 
 
 tents. Human embryos which, according to His's data/ are some- 
 where about the 30th day of intrauterine life, betray the likeness 
 in a striking degree. Specimens at this age are nearly com- 
 parable to thirteen days' rabbits, or to chicks at the end of the 3rd 
 day. Their newly budded limbs have none of the bends they 
 ultimately attain, nor can digits be discerned ; moreover, the 
 crystalline lens is incompletely formed and still united to its 
 parent epiblast. A transverse section through such an embryo 
 as this has already been figured and described (p. 4, jSg. 2), 
 so nothing further need be said before dealing with the details 
 of the various structures. The way in which the Wolffian duct 
 ends anteriorly, and the relation of the tubules to the peri- 
 toneum may be ascertained, but the earlier stages of their 
 development can only be inferred. For the sake of clearness, 
 the description of the posterior termination of the Wolffian 
 duct may be deferred, and for the present only its course and 
 anterior termination considered. After all that has been said, 
 it suffices to say that it runs forward in the urogenital ridge 
 lying beneath its epithelium. Of course, in these respects it 
 resembles the Wolffian duct of the rabbit and chick, and it in 
 no way differs from them, unless, perhaps, in being situated a 
 little nearer the front of the ridge (Plate I. fig. 2). 
 
 So far, little has been said about the germinal epithelium 
 which covers the urogenital ridge, because rabbits' embryos 
 have chiefly been described, and in that animal its characters 
 are not very distinctive. However, in the chick the germinal 
 epithelium is represented by a semiliine of columnar and large 
 ovoid cells, which surrounds the most convex part of the ridge, 
 and is continuous by its tapering ends with the rest of the lining 
 of the body cavity. The huma.n embryo has germinal epithelium 
 arranged like that of the chick, and its appearance is shown in the 
 accompanying figure, which has been drawn from the front part 
 of the Wolffian body of an embryo at about the 30th day of 
 intrauterine life (fig. 17).^ 
 
 In human embryos the front ending of the Wolffian duct is 
 the same as in the rabbit or chick, and is found in the same 
 
 ^ Loc. cit., part iii. p. 238 ; Atlas, part iii. plate x. figs. 9 to 12. 
 2 The germinal epithelium of the human embryo and of the rabbit is des- 
 cribed in Lecture II. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 27 
 
 position, behind the lungs, and close to the venous end of the 
 heart. In this region the urogenital ridge and germinal epi- 
 thelium have almost dwindled away, but the cardinal vein shows 
 where the duct may be found, or rather where the column of 
 cells which represent it may be found, because it is very ques- 
 tionable whether the terminal part has any lumen. However, 
 the ending is independent of the peritoneal epithelium, and lies 
 between the latter and the cardinal vein (fig. 18). The next 
 question is, whether the epithelium of the human Wolffian 
 tubules is connected with the peritoneal epithelium ? and a 
 section from the same embryo, but taken a little further back, 
 allows an affirmative answer (fig. 19). At the level of the 
 section the urogenital ridge and germinal epithelium are both 
 very distinct, and the Wolffian duct may be seen lying beneath 
 the latter. But the most striking and interesting feature is a 
 Wolffian tubule which is united by one end to the germinal 
 epithelium, whilst the other dilates and encloses a large glo- 
 merulus. Between these points the tubule is narrow, but has 
 a distinct lumen, which, in this specimen, can hardly be said 
 to open into the body cavity. Nevertheless, the histological 
 arrangement suggests very strongly that there may have been 
 an opening, and likewise betokens a distinct resemblance to the 
 anterior Wolffian tubules of the chick and rabbit. 
 
 This part of our subject has enough importance to warrant 
 the production of more evidence concerning it. With this 
 object the fore part of the Wolffian body of another human 
 embryo has been delineated (fig. 20). The specimen from 
 which this was taken was very like the last, which had, it may 
 be remembered, budding limbs and a commencing crystalline 
 lens, and was compared to a thirty days' embryo figured by 
 His.^ In this case there is a very distinct inturning of the 
 peritoneal epithelium, and the nephrostoma which it forms has 
 the appearance of opening into the Wolffian duct.2 A third 
 human embryo, a little more advanced than the last two, 
 afforded valuable confirmatory evidence of the junction of the 
 
 1 His, loc. ciL, p. 239 ; Atlas, pt. 3, pi. x. fig. 9. 
 
 ^ Since the genital eminence of this human embryo has probably appeared, 
 this epithelial ingrowth might possibly be the opening for the oviduct (Miiller's 
 duct), but this supposition will prove unlikely when the development of that 
 canal is discussed in Lecture II. 
 
28 PROFESSOR C. B. LOCKWOOD. 
 
 peritoneal epithelium with that of the tubules, and perhaps 
 with the duct of the Wolffian body. So far, nothing but the 
 knowledge gained from transverse sections has been brought 
 forward, but the longitudinal sections of another human 
 embryo are so interesting, that a brief allusion to them may 
 not seem out of place. After so much repetition, it is needless 
 to describe in detail the excretory organs of this embryo. Its 
 head had been broken off before it came into my possession, 
 but as its limbs had just budded I judged it had attained 
 about the 30th day of intrauterine life, and of course the histo- 
 logical features assisted me in arriving at this conclusion. The 
 interest of the specimen centred in the forepart of the Wolffian 
 body, where three vascular bulbous projections jutted into the 
 body cavity. The free end of each of these (fig. 21) is covered 
 with a layer of cylindrical cells, longer than those which cover the 
 adjacent surfaces. The characters of these projections are very 
 definite, but their size varies. The hindermost is the largest 
 and most vascular, and then comes its next door neighbour ; but 
 the foremost prominence, that nearest the head, is quite short, 
 and by no means so obvious as the others. Between the largest 
 of these protrusions, or, in other words, between the middle and 
 posterior, there is a deep recess which, in some sections, seems to 
 open into a neighbouring Wolffian tubule (fig. 22). Unfortu- 
 nately it is impossible to make an unqualified statement upon 
 this point, but at all events the epithelial lining of the recess is 
 continuous with that of the tubule. Human embryos seldom 
 afford very perfect material, so that, as in this instance, although 
 the outstanding processes are quite clear and distinct, yetthe com- 
 munication between the tubule and body cavity is not so certain. 
 However, the appearances seen in these longitudinal sections 
 acquire fresh significance when they are considered by aid of the 
 information obtained from those which are transverse. Without 
 doubt, after a while the human Wolffian tubules will be demon- 
 strated as clearly in continuity with the peritoneal epithelium 
 in longitudinal as they have been in transverse sections. 
 
 The actual nature of these villous-looking protrusions is hard 
 to determine. It is impossible to ignore their likeness to the 
 external glomeruli of the pronephros of the chick, and it is by 
 no means impossible that a similar organ is in question. On 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 29 
 
 d priori grounds such an assumption is tenable, and I am in- 
 clined to think that the human embryo may have a rudimentary 
 pronephros. Speaking relatively, the human embryo, that in 
 which the protrusions into the body cavity were seen, was not 
 more developed than a chick of the third day, and, as far as 
 could be ascertained from longitudinal sections, it did not possess 
 a genital eminence. In the next lecture reasons will be adduced 
 to show that it is unlikely that the projections have anything 
 to do with the oviduct. 
 
 LECTURE II. 
 
 Glomeruli of Wolffi,an Body. 
 
 The glomeruli of the Wolffian body have been frequently 
 referred to in the first lecture, but, so far, nothing has been said 
 concerning their histology or development. This omission may 
 now be repaired, and, fortunately, suitable human embryos are 
 available for the purpose. This happens because the glomeruli 
 have just appeared in the youngest human embryo at my 
 disposal, and are still in their most primitive condition. In 
 order of development the glomeruli are not manifest until 
 after the Wolffian duct and tubules are well established ; and, 
 roughly speaking, their appearance coincides with the earliest 
 budding of the limbs ; but, preparatory to their development the 
 Wolffian tubules grow and alter. It may be best to glance 
 for a moment at that phenomenon, and then proceed with the 
 development of the glomeruli. 
 
 In Lecture I. the development of the Wolffian tubules was 
 traced until they looked as if they were hollow outgrowths from 
 the duct, and in this early stage their length was insignificant, 
 and they only reached from the inner side of the duct as far as 
 the peritoneal epithelium. But afterwards the tubule elongates, 
 and, by the time the glomerulus has appeared, is slightly bent. A 
 typical tubule would consist of the following parts: — (1) a section 
 carrying the peritoneal opening, and known as the peritoneal 
 funnel,^ (2) a dilated vesicle into which this opens, (3) a coiled 
 J. 1 Foster and Balfour, 2nd edit., p. 193. 
 
30 PROFESSOR C. B. LOCKWOOD. 
 
 tubulus proceeding from (2), and terminating in (4) a wider 
 portion opening into the Wolffian duct.^ Evidence has been 
 adduced to show that the human embryo, as well as the rabbit, 
 has at the fore end of its Wolffian body peritoneal openings or 
 nephrostomata, but these will not be mentioned again, because this 
 portion of the organ totally disappears, and has nothing whatever 
 to do with the events which follow. But the tubules do not pre- 
 sent, either in the rabbit or in the human embryo, any peculiarity 
 at their opening into the Wolffian duct ; but towards its other 
 extremity there is a dilatation, into which a bunch of capillaries 
 grows to form a glomerulus. It therefore follows that all the 
 human embryo ultimately possesses of the four divisions of a 
 typical tubule is (1) a coiled canal and (2) its dilated glomerulus- 
 containing part. But we must not forget that in one of the 
 transverse sections of a human embryo of the thirtieth day of 
 intrauterine life a very strong resemblance to the typical 
 arrangement can be traced (fig. 19, PL I.). In this case 
 the tubule running from the peritoneal epithelium and end- 
 ing at a large glomerulus is of the greatest significance, and 
 seems to represent a "peritoneal funnel." Before describing 
 the development of the glomeruli, the manner of growth of 
 the tubule calls for inquiry, and at the outset it is clear that it 
 can hardly take place by additions made at either end. As far 
 as can be judged, the cells which form its walls divide and 
 multiply, and in so doing increase both the length and calibre 
 of the canal they surround. 
 
 Taking both the pronephros and mesonephros into considera- 
 tion, two sorts of glomeruli may be developed in connection 
 with them. The first variety are called external glomeruli, 
 because they protrude into the pleuro-peritoneal cavity instead 
 of into the tubules. Their presence is undoubted in the chick, 
 but it is very questionable whether they exist in the rabbit, and 
 in man their development has hardly been established, although 
 I have described a specimen in which it is possible that they 
 have been imitated. However, in the absence of confirmatory 
 evidence, it would be rash to aver their existence upon such 
 
 ^ Since the first lecture was written, I have seen an exceedingly wide opening 
 between a Wolffian tubule and the pleuro-peritoneal cavity in a rabbit's embryo 
 of 9 days and 18 hours. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 31 
 
 gi'ounds as these, and therefore, under the circumstances, only 
 the other kind of glomeruli remain for examination. In contra- 
 distinction to those which have just been mentioned these are 
 named " internal glomeruli," and they protrude into the Wolffian 
 tubules. A perusal of Mr Sedgwick's i monograph shows that 
 the distinction is rather one of detail than of principle, because 
 that author satisfactorily shows that the external glomeruli 
 are simply internal glomeruli which have protruded into the 
 peritoneal cavity through greatly widened- out nephrostomata. 
 However, the names are very convenient, and deserve to be 
 retained. In future, for reasons which have just been given, 
 only internal glomeruli are in question. The accompanying 
 figure, made from a section of a human embryo at about the 
 thirtieth day, affords an idea of the appearance of one of these 
 structures shortly after its appearance. The canal of the Wolffian 
 tubule is at this time about -g^o^'^ °^ ^^ ™^^ i^ diameter, but 
 is dilated at the end which is furthest from the Wolffian duct 
 to contain the glomerulus. The latter consists of capillaries 
 surrounded by round mesoblastic cells (PI. II. fig. 23), and 
 covered, where it protrudes into the tubules, by a reflexion 
 of the lining epithelium, which consists of a single layer 
 of cubical cells. In this specimen there is no histological 
 difference between the cells which line the tubule and its 
 dilatation and those which cover the glomerulus. At this early 
 stage the glomerulus bulges prominently into the expanded 
 tubule, and is continuous by a wide base with the rest of the 
 mesoblast of the Wolffian body. However, a trace of a con- 
 striction has begun to form at the base, and this by its 
 increase will afterwards form the "neck of the glomerulus." 
 The mesoblast, which in a great measure composes the Wolffian 
 body and glomeruli, is embryonic in type and consists of round 
 nucleated cells, which are about y5'oo^^ ^^ ^^ i^^^ i^ diameter. 
 These elements have indistinct margins, and in some parts 
 protoplasmic processes unite adjoining cells. The blood-vessels 
 of the Wolffian body at this stage are not very numerous, and 
 are bounded by spindle-shaped cells; they run as loops into 
 the glomeruli (fig. 23), Whatever histological changes take 
 
 ^ Adam Sedgwick, On Early Developmen of the Anterior Part of the Wolffian 
 Duct and Body in the Chick &c. , p. 24. 
 
32 PROFESSOR C. B. LOCKWOOD. 
 
 place after this, and they are many, the anatomical arrangement 
 which has been described, a glomerulus protruding into the 
 dilatation of a tubule, does not alter, except that the glomerulus, 
 owing to a narrowing of its neck, becomes more pendent into 
 the cavity which contains it (figs. 24 and 25). As regards 
 the place at which the glomerulus protrudes into the tubule, it 
 may be noted that the invagination is not exactly at the end of 
 the tubule, but usually at one side. Of course such a trivial 
 circumstance as this hardly alters the anatomical arrangement. 
 
 After it has been established in this way, the glomerulus 
 grows larger, and the tissues of which it is made assume new 
 and altered characters. For instance, both in human embryos 
 and in rabbits, the epithelium which covers its surface changes 
 its cubical shape and becomes flattened. The cell nuclei do 
 not participate in the change but remain round and plump, 
 and bulge in a striking manner and clearly mark the margin 
 of the glomerulus (fig. 25). The layer of epithelium which 
 lines the interior of the glomerulus-containing sac, that which 
 corresponds to Bowman's capsule in the kidney, also becomes 
 flattened, except where it joins the cubical epithelium of the 
 tubule ; here it retains its original form (fig. 24). Accompanying 
 these changes in the epithelium are others in the substance of 
 the glomerulus. It has been seen that at its first appearance the 
 latter consisted of small round cells, a few of which were elon- 
 gated and bounded the capillary loop. The human embryo which 
 yielded this information was somewhere near the thirtieth day 
 of intrauterine life and had but a slight degree of perfection. In 
 another human embryo, fths of an inch long and about the seventh 
 week of intrauterine life (fig. 24, also fig. 39, p. 52), and in which 
 the limbs and fingers and toes were clearly formed, the develop- 
 ment of the glomeruli had advanced a step. During the early 
 phases the epithelial covering was easy to recognise because of 
 its cubical shape and deep staining, but in the seven weeks' 
 embryo its identity is by no means so clear, although, without 
 doubt, it is represented by some slightly flattened cells which 
 cover the surface. Moreover, the elements which form the bulk 
 of the glomerulus are bigger than they were at the thirtieth day, 
 and this seems due to an increase in the amount of the proto- 
 plasm which surrounds the nucleus. But, besides increasing in 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 33 
 
 amount, it is perceptible that the protoplasm, especially that 
 which belongs to the cells near the neck of the glomerulus, has 
 sent out branches which, by joining with corresponding processes 
 from other cells, are beginning to form a reticulated network ; 
 this reticulum is of the greatest interest and importance, and 
 will be mentioned again presently. However, the bulk of the 
 glomerulus consists at this stage of rounded nucleated cells 
 interpenetrated by a few capillaries, which seem to originate as 
 follows : — Along certain routes the embryonic cells, both of the 
 glomerulus and of the Wolffian body in general, elongate and 
 arrange themselves in parallel lines, separated by a narrow inter- 
 val into which blood from the neighbouring great vessel enters. 
 Nothing could be simpler than this process, and after originating 
 like this the vessels consist of an afferent set, running from the 
 aorta to the' glomerulus, and an efferent set, opening into the 
 great vein of the Wolffian body, the posterior cardinal vein. 
 
 If such a glomerulus as that which has been described be com- 
 pared with those of the kidney, with which every one is familiar, 
 their want of perfection is manifest. We are therefore impelled 
 to carry our inquiries further, and a human embryo whose 
 body and head together measured 1 j\ inch long, and which had 
 arrived somewhere near the tenth week of intrauterine life (fig. 
 40, p. 56), afforded a suitable opportunity. In this embryo some 
 of the glomeruli were as large, as, if not larger than, those of the 
 adult kidney, and their vascularity was remarkable (fig. 25). The 
 whole glomerulus is composed of a complicated interlacement of 
 tortuous capillaries, amongst which a few cells are intermingled ; 
 and, moreover, the epithelial elements have deviated from their 
 early cubical shape, so that both the surface of the glomerulus 
 and the interior of its capsule are lined with flattened nucleated 
 cells. By the time the glomeruli of the Wolffian body have 
 reached this stage of development their resemblance to their 
 fellows of the kidney is very obvious and needs no comment. 
 However, the comparison has an additional interest, because it 
 enables us to infer that the Wolffian glomerulus has reached the 
 period of its greatest perfection. It will be shown presently 
 that this is a stage at which few glomeruli are destined to 
 arrive. Many of those which appear during the earliest and 
 greatest development of the Wolffian body participate in the 
 
 C 
 
o4: PKOFESSOK C. B. LOCKWOOD. • 
 
 atrophy which overtakes the foremost part of the organ, but 
 this is a point which may be reserved for a little while. 
 
 Whilst the glomeruli have been passing through these phases 
 of development the tubules and matrix have not remained 
 quiescent. But, before speaking of these, it is important and 
 interesting to ascertain how many tubules and glomeruli the 
 human embryo may possess. Of course an exact determination 
 is hardly possible, but in longitudinal sections of the youngest 
 human embryo that has been mentioned in these pages (fig. 
 1, p. 3), and which was estimated to have arrived at the 
 twenty-third day of intrauterine life, I calculate that from 
 fifteen to sixteen tubules, and a like number of glomeruli, were 
 present. In the longitudinal sections of another human embryo, 
 also spoken of before, and estimated to have arrived somewhere 
 near the thirtieth day (PI. I. figs. 21 and 22), there seemed 
 to be from eighteen to twenty tubules and glomeruli. The 
 difference in these two cases is so small that it is evident 
 that, assuming the ages are right, an inconsiderable, or possibly 
 no new development of extra tubules or glomeruli takes place 
 between the twentieth and the thirtieth day of intrauterine life. 
 In a third human embryo which has been mentioned already 
 (p. 32), and which was estimated to have reached nearly the 
 seventh week of intrauterine life, it is hard to say whether the 
 number of glomeruli and tubules has increased ; although, on 
 the contrary, some of the foremost, as will be described here- 
 after, have begun to atrophy (fig. 39, p. 52). The same holds 
 good for a larger human embryo, previously mentioned (fig. 40, 
 p. 56), and whose length was 1^ inch, and whose age was 
 thought to be about the tenth week of intrauterine life ; in this 
 specimen there is no increase in the numbers of the glomeruli, 
 but a greater perfection of some, and an atrophy of others. 
 If these inferences are correct, it is clear that they establish a 
 difference between the human embryo and that of the chick, 
 for in the latter, as Foster and Balfour ^ point out, 
 
 "In addition to the primary tubules, secondary and tertiary 
 tubules are formed on the dorsal side of the. primary tubules. They 
 are differentiated out of the mesoblast of the intermediate cell mass 
 and open independently into the Wolffian duct." 
 
 ^ Foster and Balfour, 2nd edit., p. 192. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 35 
 
 Judging from the number of openings into the Wolffian 
 duct, it seems exceedingly doubtful whether in the human 
 embryo any tubules are developed after those which have been 
 described. 
 
 It follows, therefore, from what has gone before, that in the 
 human embryo the glomeruli of the Wolffian body reach per- 
 fection at a comparatively early period, probably about the 
 tenth week of intrauterine life, but even then some of those 
 which are anterior have begun to atrophy, and it may be said 
 in anticipation that this is ,the ultimate destiny of all of these 
 structures. But before this interesting topic is touched, if the 
 natural consequence of events is kept in view, other circum- 
 stances claim attention, and foremost may be mentioned the 
 relative positions of the various structures which compose 
 the Wolffian body. The situation of the duct, tubule, and 
 glomerulus are portrayed in fig. 2, p. 4, which represents a 
 human embryo at about the twenty-eighth day, or in fig. 37, 
 p. 39, which represents the Wolffian body and genital mass, 
 or sexual eminence as the latter is sometimes called, of a rabbit 
 of thirteen and a half days of intrauterine life. These drawings 
 clearly show that the duct lies towards the extreme outer limit 
 of the organ, that is to say, as far as possible away from the 
 mesentery and aorta ; the glomerulus, on the other hand, lies 
 more towards the inner side and in front, so that it is quite near 
 the base of the mesentery. It therefore follows that the duct 
 and glomerulus are some distance apart, and this interval is 
 occupied by the tortuous tubules. That part of the Wolffian 
 body which is nearest the spine contains, as was said before, 
 the vein (posterior cardinal) which carries away its effluent 
 blood. It is desirable to make a careful note of these relations, 
 because they help the interpretation of many subsequent events. 
 A word may be said in this place concerning the lining epi- 
 thelium of the various canals. In rabbits and in human 
 embryos the Wolffian duct is lined with columnar ciliated 
 epithelium during the later stages. The Wolffian tubules have 
 also a lining of regularly arranged columnar cells, and the 
 inner edge of the cells (fig. 37, p. 39) has large and irregular 
 protoplasmic protrusions. After the seventeenth day in rabbits 
 the cell lining of the tubules of the Wolffian body becomes less 
 
36 PROFESSOR C. B. LOCKWOOD. 
 
 columnar and particularly like the epithelium which lines the 
 convoluted tubules of the kidney. 
 
 Parenchyma of Wolffian Body. 
 
 The only portions of the Wolffian body which have not been 
 particularly mentioned are its epithelial covering and the 
 mesoblast which surrounds and imbeds the other elements. 
 The latter has already been mentioned indirectly in connection 
 with the connective tissue portion of the glomeruli, so that it 
 is natural to complete the account of its development. Doubt- 
 less it is unnecessary to begin anew the description of the 
 mesoblast which composes the human Wolffian body. At first 
 it consists of round protoplasmic cells, each of which possesses a 
 central nucleus. The process by which a very definite reticulated 
 stroma is developed from the round nucleated cells is quite 
 simple : their protoplasm sends out branches which unite with 
 those of adjoining cells so that at last a nucleated mesh work is 
 established. The various stages by which these alterations are 
 brought about are shown in the accompanying figures (figs. 
 23, 24, and 25), which also indicate that, besides forming the 
 reticulum, some of the cells are converted, in the manner which 
 has been described, into the walls of the various capillaries and 
 blood-vessels. Mere pictorial representations convey but a poor 
 idea of the perfection and beauty of the tissue which forms the 
 parenchyma of the Wolffian body, nor does comparison afford 
 much assistance. Its resemblance to the so-called mucoid or 
 gelatinous connective tissue,^ so far as the meshwork is con- 
 cerned, is palpable ; but here the likeness ends. To complete 
 the analogy it would be necessary to demonstrate the presence 
 of mucin in the meshwork, and it is hard to tell how this could 
 be accomplished. But, whatever the nature of the parenchyma of 
 the Wolffian body may be, the tissue which constitutes it is not 
 solely confined to that organ. The last embryo which has been 
 described, that which was supposed to have attained the tenth 
 week of intrauterine life, possesses kidneys of some perfection, and 
 the various glomeruli and tubules which go to form the organ lie 
 in an identical matrix. This observation is so much in accord- 
 
 1 Fide Klein, Atlas of Histology, 1880, p. 38. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 37 
 
 ance with the views usually entertained of the relationship which 
 exists between the permanent kidneys and Wolffian bodies that 
 there is no difficulty in its acceptance ; but in a little while it 
 will be demonstrated that, by the time it has reached a certain 
 stage of development, the body of the testis has a reticulum 
 which differs in no material degree from the parenchyma of the 
 organs which have just been mentioned, namely, of the kidney 
 and of the Wolffian body. The importance of this statement, 
 both from a developmental and from a pathological point of 
 view, will be admitted when we consider that branch of our 
 subject which treats of the development of the body of the 
 testis, and the time has now arrived at which this task may be 
 profitably and conveniently undertaken. 
 
 Development of the Body of the Testis. 
 
 The mere origin of the body of the testis is a matter of 
 general agreement. This point has been clearly determined in 
 the chick and in many of the smaller mammals, and therefore, 
 so far as they are concerned, the question does not call for 
 lengthened notice. Under the circumstances it is proposed, as 
 a preliminary, to endeavour to ascertain how the gland appears 
 in rabbits and afterwards in human embryos. When once the 
 origin of the testicle has been illustrated the development of 
 its various constituents will call for attention, and upon this 
 branch of the subject the widest differences of opinion exist. 
 It would be easy to verify this statement by reference to the 
 well-known writings of Foster, Allen Thomson, or Balfour, or 
 to the admirable epitome which Janosik gives in his recent 
 memoir. As we proceed, the different views will be indicated, 
 but at present let us confine ourselves to the question of the 
 origin of the body of the testicle. At present it is a matter of 
 common acceptation that, at their commencement, no one can dis- 
 criminate between the rudiments of the ovary and those of the 
 testicle, for I am not aware that Waldeyer's views upon this 
 point have met with acceptance.^ That author thinks that in 
 chicks a thick germinal epithelium is indicative of female sex, 
 whilst in males it is thin.^ Therefore, although at last these 
 
 ^ Eierstock und Ei, pp. 133 and 135. ^ itid., p. 137. 
 
38 PROFESSOR C. B. LOCKWOOD. 
 
 glands differ so widely, yet at first they originate from a cell 
 mass which is identical for the male or female ; and which in 
 its early stages betrays no evidence of its ultimate fate, whether 
 destined to become an ovary or a testicle. Under these circum- 
 stances a suitable name has to be found for this indifferent rudi- 
 ment, and it is usually called the sexual eminence. The sexual 
 eminence of the rabbit's embryo may be clearly seen during the 
 thirteenth day of intrauterine life. Before describing the manner 
 of its appearance it is desirable, for reasons stated before, viz., the 
 general untrustworthiness of time reckonings, to try to give an 
 idea of the perfection of these embryos. Therefore, it may be 
 said that the head and trunk together, although still curved 
 upon each other, may be estimated to be about two centimetres 
 long. The fore and hind limbs have incipient flexures ; as yet 
 they are deficient in digits, but the latter are already fore- 
 shadowed by dark parallel lines in the somewhat spatulate ends 
 of the limbs. Finally, the head and face are well formed, and 
 the eye has a well-marked lens and choroid. The internal 
 organs — the heart, lungs, liver, and intestines — are noticeable 
 objects, but the permanent kidneys have not appeared. A 
 transverse section through the middle of the abdomen of such 
 a rabbit's embryo, that is to say, one of thirteen and a half 
 days (fig. 37, p. 39), shows that the Wolffian bodies are 
 large and elaborate organs. The enlargement is in a great 
 measure due to an increase in the growth of the tubules, which, 
 besides having a larger calibre, are more tortuous ; moreover, it 
 is obvious that the gland has larger glomeruli and is more 
 vascular. The length of the Wolffian body is still very great 
 compared with that of the embryo. It reaches from the 
 diaphragm, which by this time has almost completed its 
 development, nearly as far as the hind end of the peritoneal 
 sac ; in fact, it stretches nearly the whole length of the back of 
 the abdominal cavity. In the specimen from which the draw- 
 ing was made (fig. 37, p. 39) it happens that the genital eminence 
 is already prominent, and consists of a collection of cells which 
 are heaped up towards the front and inner side of the uro- 
 genital ridge, and very near the place where the latter abuts 
 upon the base of the mesentery. At this time the bulk of the 
 urogenital ridge consists of the Wolffian body and its various 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 
 
 39 
 
 constituents. The relation of the genital eminence to the uro- 
 genital ridge may be illustrated by saying that, if the length of 
 the ridge be divided into thirds, the genital mass would occupy 
 rather more than the middle third.^ This is only an approxi- 
 mate estimate, because the eminence tapers at either end, and 
 therefore it is hard to determine its exact limits.^ 
 
 The histology of the genital eminence in its earliest stages is 
 
 Mes 
 
 WD. 
 
 Fig. 37. — Wolffian body and sexual eminence of rabbit, 13J days. W. D., "Wolffian 
 duct; C.V., cardiac vein; Mes., mesentery; A.O., aorta: G.M., genital mass. 
 
 of great interest and importance. In order to see the appear- 
 ances which are described below, sections of extreme thinness 
 are essential, and a high power, such as Zeiss, -j^th oil 
 immersion, should be used. If the section should happen to be 
 at all thick, or the power low, the genital eminence looks like a 
 homogeneous mass of cells. However, it consists of two sorts of 
 
 1 These remarks are also applicable to rats, corresponding in their development 
 to thirteen days' rabbits. 
 
 - Foster and Balfour, loc. cit., p. 221, say that at its first commencement in the 
 chick the genital eminence extends the whole length of the Wolffian body and 
 genital ridge, but subsequently is restricted to its anterior part. See also 
 Waldeyer, p. 136, who makes a similar statement. 
 
40 PROFESSOR C. B. LOCKWOOD. 
 
 elements, viz., of a stroma of large branched anastomosing cells, 
 and of unbranched cells (fig. 26) contained in the meshes of 
 the stroma. The relative proportions of branched and of 
 unbranched elements is not the same throughout. Where 
 the eminence abuts upon the Wolffian body the network of 
 branched cells predominates, and is very easy to see. It is 
 continuous with the stroma of the Wolffian body, and the 
 description which has been given to the latter applies to it in 
 nearly every particular. The protoplasm of the branched cells 
 is here and there collected into masses of some size, and where 
 this happens large granular oval nuclei, which have one or more 
 nucleoli, are usually seen (fig. 26). As the cells of the stroma 
 approach the peritoneal surface of the genital eminence they, 
 and their nuclei, become a little smaller, and there is a corre- 
 sponding diminution in the size of their meshes. At the same 
 time the stroma cells stain more deeply, and their nuclei are 
 irregular in outline. In this and other specimens (fig. 32) 
 some of the processes of the stroma are prolonged between the 
 cells of the germinal epithelium as far as its peritoneal surface. 
 As the genital eminence nears the Wolffian body its stroma 
 becomes more palpable, but near the germinal epithelium it is 
 partially obscured by a number of unbranched cell elements, 
 whose nature is to be determined by an examination of the 
 germinal epithelium. It is convenient to do this by simply trac- 
 ing the lining epithelium of the abdominal cavity over the genital 
 eminence (fig. 26). It has been said before that the peritoneal 
 epithelium, at the thirteenth day, consists of a single layer of 
 more or less cubical epithelial cells. Supposing that we look at 
 this investment as it reaches the edge of the genital eminence, 
 it may be seen that the individual cells have undergone con- 
 siderable alteration. First of all, their size is no longer uniform, 
 some being large and oval, others columnar, and not a few quite 
 small and insignificant. So far as size is concerned, a very 
 simple explanation is at hand, for a very active process of 
 multiplication by fission is going on, and the smallest cells are 
 simply those which have just been formed (fig. 26). But, 
 returning again to the margin of the genital eminence and 
 tracing the peritoneal epithelium over it, a marked alteration 
 in the disposition of the epithelium is to be observed. Instead 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 41 
 
 of being arranged in an uniform layer their depth varies, and 
 their deep surface has an irregularly festooned appearance. This 
 appearance is caused by some of the cells of the germinal 
 epithelium invading the stroma. These cells are recognisable 
 because they stain more deeply than the larger oval cells 
 which belong to the stroma, and because they have no 
 protoplasmic branches. Whether the meshes of the stroma 
 contain any other unbranched cells except these is hard to 
 decide, but, after a great deal of study, I think that if thin 
 sections are examined this question will be answered in the 
 negative. It is exceedingly hard to give an adequate idea of 
 this tissue either by description or by delineation, and although 
 I think it is possible, even from early stages, to recognise the 
 germinal cells, j^et it is to be feared that only a very inadequate 
 impression of their peculiarities has been conveyed. 
 
 It is obvious that the preceding account does not apply to 
 the very earliest beginning of the genital eminence. But before 
 attempting that topic, a few spindle-shaped cells near the base 
 of the genital eminence (fig. 37, p. 39) may be mentioned. They 
 merely bound blood-vessels which, even at the thirteenth day, have 
 entered the base of the eminence ; and they belong to the stroma. 
 
 Further knowledge of the genital eminence may be gained 
 from younger embryos, and is confirmatory of the preceding. 
 However, this part of the subject is so important that perhaps 
 it may be well to introduce it here, more especially as by so 
 doing the study of the human embryo is facilitated. In a 
 rabbit's embryo at the beginning of the thirteenth day, and in 
 which the limbs were merely short protrusions, the lining of the 
 peritoneal sac consisted of a layer of cubical cells, each contain- 
 ing a nucleus. These cubical cells were continued over the 
 urogenital ridge without exhibiting any alteration except 
 towards its inner aspect. In this situation, the spot which the 
 genital eminence afterwards occupies, the cells are slightly more 
 columnar (fig. 27) and lie at least three cells deep. Although 
 the various structures, such as tubules and glomeruli, contained 
 in this rabbit's urogenital ridge are not so perfect as they are 
 in the chick at the fourth day — the period at which Waldeyer 
 depicts the germinal epithelium ^ — yet it may be assumed that 
 
 ^ Waldeyer, Eierstoch und Ei, p. 120, assigns a much greater distribution to 
 
42 PROFESSOE C. B. LOCKWOOD. 
 
 the thickening of the epithelium seen towards tlie inner side of 
 the urogenital ridge of this rabbit is the beginning of its 
 germinal epithelium. The section from which the drawing (fig. 
 27) was made came from about the middle of the ridge, and it 
 was only in this neighbourhood that the thickening was seen.^ 
 With regard to the characters of the cells of the germinal 
 epithelium, it is to be noted that they stain freely and that 
 those next to the peritoneal sac are columnar, whilst the deeper 
 ones are more or less oval and have a conspicuous nucleus. 
 
 The tissue upon which the rabbit's germinal epithelium rests, 
 and which, of course, belongs to the urogenital ridge, consists 
 of a network of branched anastomosing cells, many of which 
 possess a large nucleus and nucleolus. The relation of this 
 tissue to the germinal epithelium is most important. Where 
 the two structures are in contact the basement line of the 
 epithelium is not apparent, more particularly where the 
 epithelium is thickest ; and the union is so close that the 
 processes of some of the branched cells are prolonged between 
 the cells of the germinal epithelium. 
 
 The conclusions which it seems reasonable to draw from this 
 account of the genital eminence of the rabbit is that that 
 structure from its commencement consists of — A, Stroma ; B, 
 Germinal Cells ; C, Blood-vessels. 
 
 Since it is quite clear from what has gone before that the 
 human embryo has a urogenital ridge and germinal epithelium 
 almost the same as in the chick or rabbit, it seems reasonable 
 to suppose that it might also possess a genital eminence, 
 and that the latter would originate in the same way as in the 
 animals that have just been mentioned. A human embryo two- 
 thirds of an inch long, and whose arms and legs were short and 
 devoid of flexures, seems to place this question beyond the stage 
 of hypothesis. A section through the middle of the urogenital 
 ridge of this specimen shows that there is a distinct elevation 
 towards its front and inner side, and not very far from the base 
 of the mesentery. This elevation mainly consists of mesoblast, 
 and it seems reasonable to assume that it represents an early 
 
 the germinal epithelium of the chick than can be seen in rabbits, or, I think, in 
 human embryos. 
 ^ Compare Waldeyer, loc. cit. , pi. v. fig. 50. 
 
THE DEVELOPMENT AXD TRANSITION OF THE TESTIS. 43 
 
 stage of the genital eminence. The arrangement of the neigh- 
 bouring epithelium bears out this assumption. Near the place 
 where the Wolffian duct lies in the urogenital ridge (fig. 28) 
 the peritoneal epithelium is nearly flat, but as it nears the 
 eminence which has just been mentioned its cells become larger 
 and more columnar, and have many of the characters of germinal 
 epithelium. In addition, the depth of the epithelium over the 
 convexity of the eminence is greater than anywhere else. This 
 thickening is due to an actual increase in the thickness of the 
 germinal epithelium, and, besides, a number of its cells are 
 mingled with those of the underlying mesoblast. These deeper 
 cells are somewhat irregularly disposed, and indistinguishable 
 from those which cover the surface. Making every allowance 
 for the nature of the material which has afforded the foregoing 
 information, I think that it would not be rash to conclude that 
 the human embryo has a genital eminence almost identical in 
 character and origin with that of the rabbit. Before taking leave 
 of the human genital eminence a word may be spoken about 
 the mesoblast which helps to form it. This tissue consists of 
 quantities of small mesoblastic cells not much larger than lymph 
 corpuscles. These elements are of various shapes — round, oblong, 
 or spindle-shaped, and each possesses a nucleus. Whether any of 
 them are branched at this early stage is hard to tell, because they 
 are all so closely crowded together, much denser than in rabbits. 
 This point having been arrived at, the next question refers 
 to certain peculiarities which are attributed to the cells of the 
 germinal epithelium. Perhaps the point at issue may be made 
 clearer by the following quotation :^ — 
 
 " This ' sexual eminence ' is present in the early stages of both 
 sexes. In both the epithelium consists of several layers of short 
 cylindrical cells, a few of which are conspicuous on account of their 
 size and their possessing a highly refractive oval nucleus of consider- 
 able bulk ; in both the underlj'iug thickened mesoblast consists — as in- 
 deed at this epoch it does generally in all parts of the body — of spindle- 
 shaped cells. The larger conspicuous cells of the epithelium, which 
 appear to have quite a common origin witii their fellow cells, and to 
 arise fi'om them by direct differentiation, and which are seen at the 
 first in male as well as in female embryos, are primordial ova or 
 primitive germinal cells. Thus in quite early stages it is impossible 
 to detect the one sex from the other." 
 
 1 Foster and Balfour, 2nd edit., p. 221. 
 
44 PROFESSOR C. B. LOCKWOOD. 
 
 Assuming that, so far as the chick is concerned, these observ- 
 ations are correct, we will now endeavour to see whether they 
 can be applied to either the rabbit's or human embryo. 
 
 After the description which has been given of the rabbit's 
 germinal epithelium it is unnecessary to institute tedious com- 
 parisons. Although that animal does not possess primitive 
 germinal cells which conform exactly to the description of 
 those of the chick, nevertheless the deeper ovoid cells of its 
 germinal epithelium may be their representatives. It is true 
 that it can hardly be said that " they are conspicuous on account 
 of their size," or that they " possess a highly refractive nucleus of 
 considerable bulk" ; but that some of the deeper cells of the 
 rabbit's germinal epithelium betray a distinct resemblance to 
 the primordial ova of the chick, and that they appear to become 
 an integral part of the genital eminence cannot be denied. 
 Moreover, speaking more particularly of ova, when it is con- 
 sidered how, at maturity, the avian ovum differs from that of 
 the mammal, ought we to wonder that their early stages are not 
 quite the same. It seems as though the ovum of the bird began 
 to assume its peculiar characters, especially largeness, from its 
 very beginning ; but that in the rabbit and human embryo the 
 germinal cells hardly acquire such a definite individuality. 
 
 The quotation raises another question, viz., the characters 
 of the mesoblastic tissue which helps to form the genital 
 eminence. It is said that in chicks at the fourth day of 
 incubation the mesoblast which underlies the germinal epi- 
 thelium consists of spindle-shaped cells ; but Waldeyer,i also 
 speaking of chicks at the fourteenth day of incubation, says that 
 the tissue in question consists of ordinary small round or flattened 
 cells joined to one another by branches, and that they are the 
 same as the connective- tissue cells which at this period are 
 found throughout the embryo. In addition, he mentions that a 
 slight augmentation of this tissue causes the elevation which 
 constitutes the genital eminence, and in his figure a colony of 
 nucleated cells is indicated in this position. The whole of this 
 description, of the correctness of which I have assured myself, 
 might be applied to the rabbit's embryo, with the exception 
 that in them there is hardly any increase in the density of the 
 
 '^Loc. ciL, p. 136. 
 
THE DEVELOPMENT AND TEANSITION OF THE TESTIS. 45 
 
 stroma which underlies the germinal epithelium. It is to be 
 understood that this statement applies to very thin and highly 
 magnified sections. In human embryos which show the 
 earliest stages of the genital eminence, the tissue subjacent to 
 the germinal epithelium is rich in cells of various shapes and 
 sizes, but, owing perhaps to the nature of the material, the 
 network of branched anastomosing cells is not perceptible ; 
 however, it is very obvious in the later stages of the develop- 
 ment of the human testicle. 
 
 It has been deemed expedient to describe the genital eminence 
 of the rabbit at some length, because, although its histogenesis 
 is most probably the same in the human embryo, yet, as I 
 have often said, the material they afford is seldom good 
 enough to serve as the basis for independent conclusions. 
 Nevertheless, it is easy to understand that, although this be the 
 case, human embryos may furnish a great deal of information 
 which is reliable when supported with evidence derived from 
 examination of other mammals. 
 
 When once the genital eminence has become established, its 
 growth proceeds apace. By the seventh week, in human embryos, 
 it is almost equal in bulk to the Wolffian body, and by the tenth 
 week is larger than that structure ; a superiority which it ever 
 afterwards maintains. But before passing to these later stages 
 it is desirable to mention some of the steps by which they are 
 reached. So far the Wolffian body, both in rabbits and in 
 human embryos, has been the main representative of the 
 excretory system. However, the definite establishment of the 
 genital mass determines an important alteration. 
 
 Permanent Kidneys. 
 
 Before this event the Wolffian body throughout its whole 
 extent seems qualified to perform the duties of a great excretorj^ 
 organ. But a time has arrived when the genital mass originates 
 and grows in its proximity, and henceforth the Wolffian body, 
 instead of fulfilling its manifest destiny — to function as an 
 excretory organ — becomes a mere appendage of the newly arisen 
 sexual gland, and eventually is the epididymis. No immediate 
 alteration in the appearance of the Wolffian body denotes this 
 
46 PROFESSOR C. B. LOCKWOOD. 
 
 change in its destiny, but nevertheless the organism has to 
 make provision for the performance of the functions for which the 
 Wolffian body has presumably become incompetent. Under these 
 circumstances, the permanent kidneys begin to originate. In a 
 rabbit's embryo at about the middle of the thirteenth day of intra- 
 uterine life, and in which the genital eminence is comparatively 
 small, and whose Wolffian body is still large, the ureter is the only 
 part of the permanent excretory apparatus which has appeared. 
 This canal springs from quite the hinder end of the Wolffian 
 duct, and running towards the head and behind the posterior 
 part of the Wolffian body, ultimately terminates in the kidney. 
 The latter organ is, as far as I have been able to ascertain from 
 the examination of numerous human embryos and many rabbits, 
 even from its earliest beginning, quite separate and distinct from 
 the Wolffian body (fig. 29). When the kidneys appear the limits 
 of the Wolffian body are very definite, and there is no admixture 
 of its canals with those of the kidney. As for pretending to dis- 
 tinguish the canals of the one organ from those of the other, it 
 would, in my opinion, be exceedingly difficult, or perhaps im- 
 possible. If these points are conceded it would seem superfluous 
 to invoke the existence of misplaced Wolffian tubules for the 
 purpose of explaining congenital cystic conditions of the kidneys. 
 Some malformation of the kidney tubules themselves, or of the 
 glomeruli, would afford an equally plausible explanation, and 
 would not necessitate a demonstration of the passage of Wolffian 
 tubules into places where they do not normally exist.^ 
 
 The permanent kidneys seem to me to originate in the rabbit 
 and rat in the manner described by Kolliker.^ Sections through 
 rabbits at the commencement of the fourteenth day, in my 
 opinion, confirm the statements of that author. After the 
 Wolffian duct has received the whole of the Wolffian tubules it 
 runs a little distance towards the tail end, and terminates in the 
 urogenital sinus. Just before its ending the Wolffian duct 
 receives a canal which closely resembles it in appearance and 
 size. This canal extends forward towards the head, pursuing 
 a course parallel to, but behind, the Wolffian duct, and when it 
 
 ij. Bland Sutton, "Erasmus "Wilson Lectures on Evolution in Pathology," 
 Lancet, 1887, vol i. p. 355. 
 
 2 Kblliker, loc. cit, p. 946, figs. 579 and .580. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 47 
 
 has arrived behind (i.e., dorsal to) the hinder extremity of the 
 Wolffian body, terminates in two or three csecal prolongations 
 (fig. 29). These latter represent the commencement of the 
 kidney, and they are lined with a single layer of columnar 
 epithelium. This lining differs from that of the ureter, with 
 which it is continuous, merely in the length of its cells : 
 instead of being short columnar like those of the ureter, they 
 are exceedingly long. Although these remarks are founded 
 upon observations made upon rabbits, I have also found that 
 they are applicable to the rat. Before leaving the subject an 
 aggregation of mesoblastic cells (kidney blastema) which sur- 
 rounds the rudimentary kidney tubules calls for remark. It 
 is present both in rabbits and rats, and gives origin to the 
 parenchyma of the organ. It is not proposed to pursue this 
 question any further at present, but perhaps enough has been 
 said to establish the independence of the permanent kidneys 
 and Wolffian bodies. By the end of the fourteenth day the 
 original prolongations from the ureter have been reinforced by 
 many others, and the permanent kidneys are well established. 
 A transverse section through an embryo rabbit, of the fourteenth 
 day after impregnation, shows the relation of the comparatively 
 well-developed kidney to the hinder part of the Wolffian body 
 and to the genital mass (fig. 30). The genital mass may be 
 seen lying to the front and inner side of the Wolffian body, 
 and immediately behind the latter is the rudimentary kidney. 
 Longitudinal sections show that by this time (fourteenth day) 
 there is in rabbits a close correspondence between the antero- 
 posterior limits of the genital mass and those of the kidney, the 
 former, of course, lying in front of the Wolffian body, the latter 
 occupying a corresponding position behind it. Moreover, by 
 this time the Wolffian body has become slightly curved, the 
 concavity of bend being towards the middle line, and embracing 
 the genital mass. For this reason it is impossible in a single 
 longitudinal sagittal section to demonstrate all the foregoing 
 points ; a series must be examined. If, for a moment, attention 
 be given to the section of the fourteen-day embryo (fig. 30), the 
 elaborate structure of the Wolffian body is evident ; tubules and 
 glomeruli may be seen in great profusion. The sexual gland 
 adheres to its inner side by a broad base, and its substance is 
 
48 PROFESSOR C. B. LOCKWOOD. 
 
 continuous with that of the matrix of the Wolffian body. Under 
 low powers the genital mass looks not unlike ordinary lymphoid 
 tissue, but highly magnilBed it consists of a very delicate stroma 
 of branched anastomosing cells with a great abundance of round, 
 unbranched, nucleated elements entangled in the meshes (fig. 
 32). A glance at the kidney is sufficient to prove its rudi- 
 mentary nature, for it consists of a collection of nucleated cells, 
 contained in a meshwork of branched, nucleated, anastomosing 
 cells, penetrated by a few tubules, offshoots from the ureter. 
 The entire independence of the kidney substance from that of 
 the Wolffian body is very obvious. 
 
 Human Genital Mass. 
 
 In the rabbit at the fourteenth day the Wolffian body still 
 reaches from the diaphragm to the pelvis, and, roughly speaking, 
 the middle third of its posterior surface is in contact with, but 
 distinct from, the developing kidney; further, it is apparent 
 that the side of the Wolffian body away from the kidney is 
 in relation with the genital gland (fig. 31).^ The next step 
 is to see how far these observations are applicable to the human 
 embryo. 
 
 In a human embryo at about the fifth week of intrauterine 
 life the genital mass, or sexual gland, was a prominent object 
 (fig. 32). It lay rather nearer the outer side of the Wolffian 
 body than is the case in the rabbit, and the section which passes 
 through its midst also divides the lower part of the kidney. 
 As far as I can judge, the Wolffian body of this embryo is 
 normal so far as its histology is concerned, but in a little while 
 a most interesting abnormality of its hinder end will be referred 
 to. However, our present object is to ascertain the relation of 
 the genital gland and Wolffian body to the kidney. It may be 
 said at once that these relations are the same as those which 
 have just been noted in the fourteen-days' rabbit, the only 
 difference being that the sexual organs are not quite so much 
 in front of the kidney as they are in that animal, but more to 
 the outer side. The sexual gland also betrays in its structure 
 another divergence. Even when examined under low powers it 
 
 1 This is more apparent in sections nearer the head than that drawn in Plate 
 II., fig. 30. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 49 
 
 is clear that many of the cells which compose it are arranged in 
 columns which radiate from the centre towards the periphery. 
 This feature was not visible in the rabbit, but in this and other 
 human embryos it is very obvious, and may indicate, I think, 
 the commencement of the seminal tubules.^ Some of the 
 sections obtained from this specimen show that a layer of 
 cubical epithelial cells covers the surface of the genital mass, 
 but, with the exception of the point which has just been 
 mentioned, and which relates to the disposition of the cell 
 elements, the histology is not quite so definite as in the rabbit. 
 The material is hardly good enough to justify very positive 
 statements, but it is quite clear the genital mass consists of two 
 sorts of cell elements ; the most conspicuous are those which 
 have been said to have a tendency to arrange themselves in 
 columns, and these are fairly large, deeply stained, unbranched, 
 nucleated cells ; the others are situated between and amongst 
 the latter ; they are nucleated, but do not stain so well, and are 
 irregular in outline, perhaps branched. It is important to 
 notice that, although the Wolffian tubules are very close to the 
 genital mass, yet they do not penetrate into its substance. 
 
 Following onwards the natural sequence of events, two 
 changes which take place at the same time would naturally call 
 for notice. One of these changes is histological, and has to do 
 with the development of the seminal tubes and those of the 
 epididymis ; the other is anatomical, and produces the mesentery 
 of the Wolffian body and testis, a structure by means of which 
 those organs become more free and mobile in the abdominal 
 cavity. 
 
 Before raising these questions it seems appropriate to mention 
 the abnormality which, as was said before, affected the hinder 
 part of the Wolffian body and genital mass of the embryo which 
 has just been described. 
 
 Fusion of Wolffian Bodies — Synorchis. 
 
 This is the earliest abnormality which has been met with 
 in these researches, and the embryo in which it was found 
 was about two-thirds of an inch Ions', and its arms and lee's 
 
 ■^ The expression " tubules " is, of course, incorrect, because these structures are 
 solid columns of cells and possess no lunien. 
 
 D 
 
50 PKOFESSOR C. B. LOCKWOOD. 
 
 were already beginning to exhibit incipient flexures. In all 
 respects this specimen seemed to be normal and in good con- 
 dition, but, at its pelvic end, the Wolffian bodies of opposite 
 sides were fused for a few sections. This part of the organ, 
 viewed in section (fig. 38, p. 50), was exactly like a horse-shoe 
 kidney. The upper part of the Wolffian body, as I have said 
 before, seemed quite ordinary, and a normal genital mass grew 
 in relation with it (fig. 31). 
 
 Fig. 38. — Human embryo sixth to seventh week. The "Wolffian bodies are blended 
 towards their hinder ends. 
 
 It is interesting to speculate upon the condition which might 
 have been found in this case had the embryo ever grown to 
 maturity. Without doubt the testes must have been united 
 to one another. Such occurrences are not unknown, but must 
 be infinitely rare. 
 
 Although systematic writers are accustomed to speak of union 
 of the testis, I am not aware of more than one really authentic 
 instance. This rare case is narrated by Geoffrey Saint Hilaire,i 
 who was indebted for the details to Breton and Charvet, both 
 of whom seem to have been very competent observers. Perhaps I 
 may quote Mr Curling's 2 translation of the paragraph, because he 
 
 ^ Geoffroy Saint Hilaire, Histoire des Anomalies, 1832, t. i. p. 542. The 
 doubtful case is by Acrell, in the Scliwed. Abhandl., t. xii. p. 19. 
 2 Curling, On Diseases of the Testis, 4th edit., 1878, p. 6. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 51 
 
 has alluded to the circumstance and adds that he believes the case 
 to be unique. " An infant was born at Vizille in 1812 : several 
 physicians consulted respecting the child's sex and were of 
 different opinions ; they decided, however, to inscribe it in the 
 registers as a girl. It died at the age of eighteen months, and 
 was dissected by Breton, who recognised a complete hypospadias. 
 The scrotum was bifid and empty; and the two suprarenal 
 capsules, as well as the two kidneys and the two testicles, were 
 joined together in the middle line. The spermatic arteries and 
 veins, vesiculse seminales and vasa deferentia exhibited nothing 
 remarkable, each half of the double testicle receiving its parti- 
 cular vessels." Curling proceeds to mention a case of synorchis 
 which Sedillot found whilst examining a recruit, but there is no 
 evidence beyond the mere surmise. Saint Hilaire also alludes 
 in doubtful terms to another case. It is evident that the account 
 which has just been quoted is wanting in many important parti- 
 culars. For instance, it is not said whether the bodies of the 
 testes were fused or their epididymes, or what relation the 
 abnormal gland had to the other abdominal contents. Under 
 ordinary conditions the mesentery separates the testes, but in 
 such circumstances as are being discussed, it must have become 
 modified. In the case depicted (fig. 38, p. 50) it is clear that 
 the Wolffian bodies fuse just behind the posterior end of the 
 alimentary canal. Curiously enough, in this embryo the kidneys 
 themselves blended for a little way at their hinder extremities, 
 but none of the other paired organs were united. 
 
 Mesorchium and Mesovarium. 
 
 As far as we have at present traced the development of the 
 genital system, either in rabbits or in human embryos, the deter- 
 mination of the sex, in spite of that which Egli^ and Waldeyer 
 have said, seems with our present knowledge an impossibility. 
 Whether the radiating arrangement of the unbranched cells of 
 the genital mass, which is seen in some human embryos, may be 
 an indication of the male sex, is of course a matter of doubt, and 
 incapable of direct proof However, the events which now occur 
 speedily set all doubts at rest. Whether the embryo is destined 
 1 Egli, Th., Beitrage zur Anat. unci EntiuicMungsgeschichte der Geschkchts- 
 organe, Zurich, 1876. 
 
52 
 
 PROFESSOR C. B. LOCKWOOD. 
 
 to belong to the male or female sex has no influence upon the 
 alterations which take place in the relations of the Wolffian 
 body to the dorsal wall of the abdomen, or in the alterations 
 which take place in the relations of the genital mass to the 
 Wolffian body. Important modifications take place in these 
 particulars, either in males or females, and since they are far 
 advanced long before the histological details of the sexual organs 
 are perfected, I will consider them first. 
 
 AW 
 
 MM 
 
 A. TV.., 
 W.T.. 
 
 Fig. 39. — Human embryo (seventh week) ; section towards middle line, 
 portion of Wolffian body which, atrophies; G.M., genital mass; 
 Wolffian tubules; W.D., Wolffian duct; M.D., Miillerian duct. 
 
 The process by which the genital mass is constricted from the 
 Wolffian body, and by which the latter is freed from the dorsal 
 wall of the abdomen, takes place almost directly after the geni- 
 tal mass has appeared. A glance at fig. 37, p. 39, which was made 
 from a transverse section through the genital eminence of a 
 rabbit during the thirteenth day of intrauterine life, shows a faint 
 
THE DEVELOPMENT AXD TRANSITION OF THE TESTIS. 53 
 
 constriction at the junction of the genital mass with the Wolffian 
 body ; and, moreover, the latter, in proportion to its size, pos- 
 sesses a narrower dorsal attachment. Although these parti- 
 culars are not so obvious in fig. 31, which was made from a 
 transverse section through a human embryo of about the fifth 
 week, yet indications of their presence are not wanting. How- 
 ever, on the fourteenth day the Wolffian body of the rabbit 
 possesses a broad but distinct mesentery of its own (fig. 30), 
 and the same statement holds good for human embryos which 
 have reached somewhere near the sixth week of intrauterine 
 life. In transverse sections made through human embryos at 
 that period the Wolffian body has a well-marked mesentery, 
 which is attached to the dorsal wall of the abdomen just ex- 
 ternal to the kidney, and in addition there is an obvious con- 
 striction between the Wolffian body and genital mass. Both 
 in human embryos and in rabbits the processes which have 
 commenced in this manner continue to progress, until at last 
 the Wolffian body has a distinct mesentery, which becomes the 
 mesorchium or mesovarium, and the genital mass is merely 
 fastened to the Wolffian body by a narrow neck (fig. 39, p. 52), 
 
 The changes by which a mesentery is formed for the Wolffian 
 body and genital mass occur in exactly the same way in either 
 the male or female sex, but whilst they are taking place the 
 histology of the genital mass has undergone great alterations, 
 and moreover the Wolffian body has been profoundly modified. 
 
 Development of Tubuli Seminiferi. 
 
 Perhaps it will make that which follows clearer if I begin 
 by pointing out the order in which the process of develop- 
 ment will be followed. It is quite unnecessary to premise 
 that the genital mass, although at first seemingly indiffisrent 
 and suitable for conversion into either ovary or testicle, 
 becomes transformed either into a highly complicated tubular 
 organ or into a cell-laden mass. It is not proposed in this 
 place to discuss the conversion of the genital mass into an 
 ovary, but to endeavour to show how it gives origin to the 
 connective tissue and tubules of the testicle, and how the latter 
 acquire their needful efferent channels. Although human 
 
54 PROFESSOR C. B. LOCKWOOD. 
 
 embryos are obtainable suitable for showing the larger details, 
 nevertheless they are rarely good enough to demonstrate the 
 more minute histological changes. It is not necessary on this 
 account to repudiate them altogether, but it makes it desirable 
 to check all conclusions drawn from them by the examination 
 of more reliable material. Under these circumstances the his- 
 tology of the developing testicle of the rabbit will, first of all, 
 be mentioned, and afterwards the development of the human 
 testicle will be illustrated. But, as we proceed, it will be found 
 that rabbits need only be used in the earliest stages, and that 
 for the final ones human embryos of a satisfactory character are 
 at hand. 
 
 We have already described the formation of the genital 
 eminence of the rabbit in its earliest stages. It is unnecessary 
 to recapitulate either its mode of origin or its relation to the 
 Wolffian body. It will suffice to recommence the consideration 
 of its histological structure by referring to the appearance which 
 it presents during the first half of the thirteenth day. Since 
 these have been described in detail, they only call for brief 
 allusion. It may be remembered that from its earliest com- 
 mencement the genital eminence consisted of a network of 
 branched anastomosing cells, which was continuous with the 
 stroma of the Wolffian body. The meshes of this network con- 
 tained numerous nucleated unbranched cells, which were in con- 
 tinuity with, and the same as, the germinal epithelium (fig. 26). 
 The part of this account around which a great deal of con- 
 troversy turns is the exact relation of the cells of the germinal 
 epithelium to the rest of the genital eminence. Kolliker ^ states 
 his belief that the germinal epithelium only gives origin to the 
 ova and to Mtiller's duct ; but, at the same time, he says that 
 many authors think that it has a much greater rSle to play. 
 The preparations from which the preceding account was written 
 were exceedingly successful, and, in my opinion, showed that the 
 germinal cells penetrated almost half-way towards the base of 
 the genital mass. The embryos had been stained in picro- 
 carmine, by which the germinal cells were deeply coloured — 
 much more deeply than those of the stroma. Janoeik gives a 
 description very similar to that which I have endeavoured to 
 
 1 P. 959. 2 p^ 147 et seq. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 55 
 
 set forth ; but that author does not, in my opinion, lay sufficient 
 stress upon the stroma of the genital mass. He has compiled 
 an excellent epitome of the opinions held by many recent 
 authors. 
 
 Although at the beginning of the thirteenth day the germinal 
 epithelium of the rabbit has those appearances, nevertheless at 
 the fourteenth day it still looks almost uniform in structure. 
 Transverse sections made through the genital eminence during 
 the latter period show that its surface is covered with a layer 
 of small cubical cells, and that its bulk consists of a network 
 of branched anastomosing cells, with a number of unbranched 
 nucleated cells in the meshes (fig. 32). There is no feature 
 about the histological appearance of these unbranched elements 
 to positively identify them with the germinal cells ; we can only 
 assume, from the preceding observations, that they have been 
 derived from that source. Whilst in this indifferent stage the 
 genital mass, when looked at with a low power, is very like 
 lymphoid tissue. Even high powers do not dissipate this impres- 
 sion, more particularly as regards the stroma; but the cells in the 
 meshes do not at all resemble lymph cells; they are larger, and 
 have a more clearly defined nucleus, and a larger quantity of 
 protoplasm. 
 
 Although human embryos are seldom good enough to de- 
 monstrate such minute histology as that which has been 
 described, nevertheless the genital mass of a human embryo 
 (fig. 39, p. 52) of about the seventh week was almost the same as 
 that of the rabbit at the beginning of the fourteenth or end of 
 the thirteenth day. Both as regards stroma and unbranched 
 cells the similarity is quite clear. 
 
 Remembering that the genital mass consists of a network of 
 branched anastomosing cells, in the meshes of which are num- 
 bers of round nucleated elements, we may now proceed to ob- 
 serve how the seminal tubules originate in this tissue. The 
 commencement of the process may be seen in the rabbit's 
 embryo during the fourteenth day. About this time an altera- 
 tion may be noticed in the tissue which underlies the surface 
 layer of cubical epithelium. This change consists in a more or 
 less complete disappearance of unbranched cells from the stroma 
 in this situation, and in the stroma itself forming a narrow peri- 
 
56 
 
 PROFESSOR C. B. LOCKWOOD. 
 
 pheral zone, which differs from the central part in the smaller 
 and more elongated character of its meshes (fig. 32). This 
 layer, which represents the commencement of the tunica albu- 
 ginea testis, is arranged with the long axis of its meshes parallel 
 to the surface epithelium. Towards the centre of the sexual 
 gland other alterations may be seen in the stroma, for its meshes 
 
 Fig. 40.— Relation of testis T. and Wolffian body to kidney K., ilium II., and 
 to the front wall of abdomen ; H., beart. 
 
 have in places become exceedingly large, so that aggregations 
 of the unbranched cells are observable. That this betokens the 
 beginning of the seminal tubules will, I think, be conceded after 
 the testicle of a human embryo of about the tenth week has 
 been described. Before entering upon these particulars it may 
 be as well, for reasons which have frequently been stated, to 
 give a brief account of that specimen (fig. 40). The length of a 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 57 
 
 longitudinal section through the body and trunk was one inch 
 and three-sixteenths, the limbs were well formed, and possessed, 
 besides proper joints, well-marked fingers and toes. The testes 
 and Wolffian bodies lay in contact with, but posterior to (i.e., 
 below, in the erect posture), the kidneys ; and as this is a point 
 which will be discussed further on, we may now proceed to 
 examine the histological structure of i^e testes. 
 
 At this stage of development the sexual gland has the general 
 contour of the perfect organ and the Wolffian body has begun 
 to have a likeness to the epididymis. The surface of the testicle 
 is covered with a layer of cubical epithelium, and its interior is 
 made of a stroma of large branched anastomosing cells and of 
 numerous unbranched nucleated elements. The epithelial 
 covering has no peculiarity, and may therefore be passed over ; 
 
 
 
 
 Fig. 41. — Section through testis at tenth week to show developing seminal tubules 
 and stroma. Ep., epithelium; T.A., tunica albuginea ; St., stroma; T.T., 
 tubuli testis, x 250. 
 
 but the arrangement of the other constituents, more particularly 
 of the unbranched cells, is very interesting. If the microscopical 
 examination is begun with a low power, such as a third of an 
 inch, it is easy to see a rudimentary tunica albuginea beneath 
 the surface, and this is developed, as in the rabbit, by the 
 meshes of the stroma becoming parallel to the surface epithelium, 
 and by the disappearance of unbranched cells from its meshes. 
 Throughout the rest of the gland the stroma, under low powers, 
 has no peculiar feature. If now we pass on to the unbranched 
 
58 PROFESSOR C. B. LOCKWOOD. 
 
 cells, or, as in future they may be called, spermatic cells, it will 
 be found that, instead of being uniformly scattered throughout 
 the testicular stroma, they have disposed themselves along 
 certain paths. The irregular columns which have thus originated 
 have an arborescent appearance, which indicates that they are 
 the commencement of the seminal tubes (fig. 41, p. 57). As 
 these rudimentary tubules approach the tunica albuginea they 
 loop backwards again towards the centre of the testicle. More- 
 over, near the junction of the testicle with the Wolffian body, 
 or, as in future it may be called, the isthmus testis, the con- 
 verging tubules are joined to one another by numbers of sper- 
 matic cells, which are irregularly arranged along the long axis 
 of the testicle, and represent the rete testis (see also fig. 33). 
 
 Placing aside, for the moment, the development of the efferent 
 channels of these newly developed tubules, we may proceed to 
 consider the more minute histological characters. For this 
 purpose an amplification of about 250 diameters is enough, and 
 what follows relates to the testicle of a human embryo at about 
 the tenth week of intrauterine life seen with such a power 
 (fig. 41, p. 57). So far as its general arrangement is concerned 
 the stroma is the same as that which has been described already 
 in the developing testicle of the rabbit. But it is to be noted 
 that the strands which form the meshes of the stroma are a great 
 deal thicker. 
 
 Moreover, the thickness of the strands of the stroma is not 
 the same everywhere ; they are thinnest towards the periphery, 
 but become thicker towards the isthmus testis. Near the 
 tunica albuginea it is easy to see that any particular portion of 
 the testicular stroma is made of branched anastomosing cells, 
 which possess large, granular, oval nuclei and nucleoli ; but as 
 the strands of the stroma approach the isthmus it is clear that, 
 although its individual cell elements are the same, yet their 
 relations to one another have altered. The alteration is in the 
 shape of the cells, which, instead of being provided with long 
 and tenuous branches, have either none at all, or, in their place, 
 thick and short protrusions of their substance, and these are con- 
 tinuous with other cells. Owing to these modifications there 
 are places near the isthmus testis and near the rete where the 
 stroma is made of strands of cells which seem to possess no 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 59 
 
 branches, and which, lying side by side, closely resemble 
 endothelial plates. Where this is the case it would be easy to 
 mistake the unbranched stroma cells for endothelial plates, but, 
 even where the likeness is strongest, traces of a meshwork are 
 here and there discoverable. These appearances have been 
 particularly mentioned because of their importance when taken 
 in relation with certain columns of cells which have been observed 
 in hilum of the mature testicle. Dr Klein ^ describes and figures 
 certain " interstitial epithelial cells " in the hilum of the mature 
 testicle of the cat, and attributes them to the tubules of the 
 Wolffian body, of some of which he considers them to be the 
 remains. Judging from Dr Klein's very beautiful figure, and 
 from specimens of cats' testicles, the structures in question look 
 to me much more like the cells of the developing stroma, such 
 as I have just described. This is not intended to imply that no 
 tubules from the Wolffian body enter the hilum of the testicle 
 (or ovary), and in that which follows evidence will be forthcoming 
 upon this point. 
 
 Before taking leave of the stroma of this testicle, it is hardly 
 necessary to do more than mention that it is continuous at the 
 isthmus testis with the stroma of the Wolffian body. The latter 
 has already been depicted and described (fig. 25), and calls for 
 no further mention. It only differs from the stroma of the body 
 of the testicle in not forming strands, and in an absence of 
 collections of endothelial-looking stroma cells, such as have just 
 been alluded to. 
 
 The next question that demands attention is the histology of 
 the developing seminal tubules, and of the spermatic cells which 
 compose them. If a clear idea has been conveyed of the rudi- 
 mentary testicular stroma this should prove an easy task. The 
 spermatic cells stain more deeply than those of the stroma, and each 
 one has a central nucleus and nucleolus. Their shape is round 
 or oval, and they have no branches whatever. It has been said 
 that the spermatic cells are arranged in irregular arborescent 
 columns, and now, under high powers, it is seen that these 
 columns lie in irregular spaces in the stroma (fig. 41, p. 6 7). These 
 latter are not anything special, and merely look like enlarge- 
 ments of the meshes of the stroma ; but the outline of their 
 ^ Klein, Atlas of Histology, p. 2G9 and 286, pi. xxxix. fig. 3. 
 
60 PROFESSOll C. B. LOCKWOOD. 
 
 walls is more regular and definite, and the cells which form 
 their boundaries are usually flat or spindle shaped (fig. 41, p. 57). 
 
 The columns of spermatic cells which lie in these spaces have 
 no particular arrangement, but their tendency seems to be to 
 occupy the centre, and not to lie in contact with its walls. 
 However, it is most interesting to observe that, whilst in this 
 rudimentary state, the spermatic tubules are solid, and com- 
 posed of small round or oval cells arranged without any 
 particular order. 
 
 Owing to the kindness of Mr Hy. Butlin and Mr A. Bowlby 
 I have had the opportunity of examining histological sections of 
 sixteen malignant tumours of the testicle. It was impossible 
 to ignore the great likeness of their tissues to those of developing 
 testis. A stroma of branched anastomosing cells was visible in 
 portions of many of them, and their unbranched elements were 
 practically indistinguishable from the unbranched spermatic 
 elements which have just been described. In none of these 
 malignant tumours could I discover, even after several careful 
 examinations, any elements to which I myself should apply the 
 term " epithelium." On the contrary, specimens which would 
 accord with the definition of a cancer seem to do so because 
 their unbranched elements were collected into irregular columns, 
 like developing seminal tubules.-^ With regard to the existence 
 of epithelium in tumours of the testicle the foregoing statement 
 requires to be qualified to this extent, namely, that I have more 
 than once seen in them tubules or loculi lined with a single 
 layer of columnar epithelium. However, in those cases there 
 was no real resemblance to any ordinary form of carcinoma, and 
 the tumours usually contained cartilage and other mesoblastic 
 elements. 
 
 If the order of development was strictly followed the Wolffian 
 body would again claim attention. That organ has, whilst the 
 body of the testicle has been developing, undergone great 
 changes, and is in course of being converted into the epididymis. 
 But to avoid leaping from one branch of the subject to another 
 it is more convenient to carry the development of the body of 
 
 ^ E. Rindfleish, Lehrhitch der Patholog. Gewehelehre, Leipzig, 1886, p. 579, 
 quotes from Birch-Hirschfeld, " that the cells, as in cancers of kidney, liver, 
 breast, and testicles, come from the epithelium of the gland canals. " 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 61 
 
 the testicle a stage further, and then return to the Wolffian 
 body. 
 
 We have just seen that the seminal tubules of the human 
 embryo, and also the rete testis, are laid down as early as the 
 ninth or tenth week of intrauterine life, so that it only remains 
 to trace their future modifications. 
 
 The appearance of the human testicle at the third month has 
 been figured in the accompanying sketch (fig. 33). The seminal 
 tubules are more numerous and thicker, and the rete testis is 
 very much better marked than in the younger embryo. This is 
 due to an increase in the numbers and in the size of the sper- 
 matic cells. Both the seminal tubules and the rete testis are 
 solid columns of unbranched, deeply staining, nucleated cells. 
 Evidently the term " tubule " ought not to be applied to these 
 structures until they have acquired a lumen. At the sixth 
 month of intrauterine life the arrangement of the spermatic 
 cells has not altered, but the seminal tubules are larger, and 
 have begun to be exceedingly tortuous. I have no exact infor- 
 mation as to when the centre of the seminal columns begins to 
 clear, but in the testicle of a young goat, six months old, there 
 was a very slight indication of a clearing towards the axis of the 
 column. 
 
 The phases through which the connective-tissue stroma of the 
 developing testicle passes are comparatively simple. Although 
 up to the tenth week the stroma of the human testicle consists 
 of branched elements, yet by the twelfth week the cells are in 
 places elongated and beginning to be spindle shaped (fig. 33) ; 
 by the fifth month they have advanced a long way towards being 
 fibrous tissue, and, of course, this is its ultimate destiny (fig. 35). 
 As for the interstitial cells, which may be seen in the stroma of 
 well-prepared sections of adult testicle, it has been said that 
 they are formed from remains of the Wolffian body. The time 
 has now arrived at which we may conveniently endeavour to 
 ascertain the relation of the tubules of the Wolffian body to 
 those of the testicle ; and as this important branch of the sub- 
 ject is followed, light will be thrown upon this important and 
 interesting question. 
 
 As suitable material is at hand, I propose to confine the rest 
 of this description to human embryos. But, before enteriug upon 
 
6'2 PROFESSOR C. B. LOCKWOOD. 
 
 particulars, it is desirable to endeavour to convey an idea of the 
 general appearance and relations of the genital mass at the time 
 when the changes which are about to be mentioned begin. In 
 a human embryo five-eighths of an inch long, and at about the 
 seventh week of intrauterine life, the Wolffian body and genital 
 mass lay near the lower end of the kidney, and just overlapped 
 that organ. The genital mass was in the indifferent stage, and 
 it is impossible to be sure of its ultimate fate ; it is attached to 
 the middle third Wolffian body by a narrow isthmus (fig. 39, p. 61). 
 The Wolffian bodies themselves are not by any means so parallel 
 to one another as when first developed, and lie obliquely, with 
 their lower ends converging. There is no difficulty in observing 
 that its structure has undergone great alterations. If we begin 
 with a section near the middle line, and therefore dividing its 
 lower part, it is evident that the foremost glomeruli, although 
 larger, are faintly stained, and their tissues granular, — appear- 
 ances which indicate that they have begun to degenerate 
 and atrophy. The tubules, on the other hand (fig. 39, p. 52), 
 are exceedingly perfect ; their lumens are capacious, and 
 their lining membrane of short columnar epithelium is very 
 distinct (see also figs. 24 and 25). Turning now to a section 
 which divides the upper and outer part of the Wolffian body, 
 quite a different sort of tubule comes into view (fig. 34). 
 These may be said to begin in a collecting tube, which is a 
 continuation forwards of the Wolffian duct. I have purposely 
 refrained from calling this the Wolffian duct, to mark that its 
 characters are decidedly dissimilar, being smaller, and having 
 hardly any lumen. The tubules, which extend from the collect- 
 ing tube into the hilum of the genital mass, are still more re- 
 markable. In this and other specimens about twenty tubules 
 leave the collecting tube at right angles, and extend into the 
 hilum of the genital mass. At their beginnings these canals 
 have hardly any lumen, but they expand as they run on- 
 wards, and gradually acquire one. Their epithelium is peculiar 
 in that it stains exceedingly dark, and in being smaller and- 
 more cubical than that of ordinary Wolffian tubules^ (fig. 34). 
 When we consider the course and the relation of these peculiar 
 
 ^ The sexual canals of tlie human "WolfBan body require to be studied in suit- 
 able transverse sections, and this would, I am sure, throw light upon their origin. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 63 
 
 tubules to the genital mass, it does not seem unreasonable to 
 suspect that they are the commencement of the tubuli effer- 
 entia. Waldeyer has given semi-diagrammatic representations 
 of these tubules ;^ the human embryo which he used was 
 9 cm. long, and therefore much older than that which I have 
 been describing. Waldeyer divides the Wolffian body into two 
 parts : a sexual, consisting of these tubuli efferentia ; and a 
 urinary, consisting of the more capacious tubules and glo- 
 meruli. At present we are not concerned with the female type, 
 but it may not be out of place to note in it the destination 
 of the genital mass, and of the sexual and urinary parts of 
 the Wolffian body : the genital mass becomes converted into 
 the ovary ; the sexual part of the Wolffian body remains as the 
 structure which Waldeyer calls the " Epoophoron " ; and the 
 urinary part also persists, and is called by the same author 
 the " Paroophoron." The terminology of these remains is ex- 
 ceedingly confused. Authors have not always drawn a clear dis- 
 tinction between the sexual and urinary portions of the Wolffian 
 body. The former, as we have seen, are smaller, straighter, and 
 less canalised than the others, and have apparently no glomeruli ; 
 moreover, they penetrate into the genital mass. The urinary 
 tubules are larger, have a wider lumen, and end in glomeruli, 
 and do not penetrate the genital mass (fig. 39, p. 52). In order 
 to avoid ambiguity, a provisional list of the various names which 
 are commonly applied to these various structures is appended, 
 and has been compiled from the books of Henle, Kolliker, 
 Quain, Waldeyer, &c. 
 
 PROVISIONAL LIST OF NAMES. 
 
 In Female. In Male. 
 
 Genital mass becomes Ovary. Testicle. 
 
 Wolffian body becomes 
 
 (Epoophoron of Waldeyer. ^ C Epididymis and its 
 Parovarium of Kobelt. f = l ^^sa. efferentia or 
 
 Organ of Rosenmiiller. J ( Coni vasculosi. 
 
 SA. Paradidymis of 
 Waldeyer, or 
 Organ of Giraldes. 
 B. Vasa aberrantia. 
 
 Before I endeavour to trace the process by which, in the 
 ■^ Eierstock und Ei, p. 142, also plate vi. figs. 60 and 61. 
 
64 PROFESSOR C. B. LOCKWOOD. 
 
 male, the sexual tubules of the Wolffian body become vasa 
 efFerentia, a peculiarity which they betray during the indifferent 
 stage may be noticed (fig. 34). Where these tubules open 
 into the collecting tube they are small, and have hardly any 
 lumen, but as they run towards the hilum of the ovary they 
 expand, and have at last a considerable dilatation (fig. 40). 
 
 The meaning of this seems obscure, and, as far as I am aware, 
 has not been noticed before. However, Waldeyer made his 
 semi-diagrammatic figures from older human embryos, and I have 
 reason to think that in them the dilatation is not discernible. 
 
 The sex of the embryo from which the foregoing observations 
 were made could not be distinguished. Its genital mass was 
 in the indifferent stage, and had neither tunica albuginea nor 
 the rudiments of seminal tubules, and therefore it affords no clear 
 evidence of the way in which a communication is effected between 
 the tubules of the Wolffian body and those of the testicle. 
 The human embryo of about the tenth week may carry us 
 a step further (fig. 40, p. 56). This embryo has already been 
 mentioned, and the development of the body of its testicle has 
 been traced up to the point at which it consisted of solid arbor- 
 escent columns of cells converging to a rete testis all imbedded 
 in a stroma of branched anastomosing cells, and surrounded, 
 except at the isthmus, by a tunica albuginea. The Wolffian 
 body of the embryo, like the last, consisted of two portions 
 distinguished by the dissimilarity of their tubules ; these parts 
 being, of course, those which have been called the sexual and 
 the urinary. The urinary part of the Wolffian body, if we may 
 judge from the perfection of its structure (fig. 25), is at the 
 height of its development, and in size far exceeds the sexual 
 part. This latter contains the curious tubules which have just 
 been described and identified with the vasa efferentia. They 
 are a quarter the size of the urinary tubules, and their 
 epithelium stains darkly ; they run nearly at right angles from 
 the collecting tube, and extend into the hilum of the testicle, 
 where they are slightly dilated, and have a lumen. With regard 
 to this last point it is interesting to note that it is exceedingly 
 hard to say whether either the foremost part of the collecting 
 tube, or the portions of the tubules (tubuli efferentia) nearest 
 to them have a real lumen. However, in the hilum of the 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 65 
 
 testicle the latter are canalised, and some of them contain a 
 structureless substance, which stains faintly, and is doubtless 
 some form of secretion. This embryo is, without question, of 
 the male sex, and it shows, at least, that the sexual tubules 
 reach the body of the testicle. 
 
 But, before it is possible to form any conception of the way in 
 Avhich the sexual tubules of the Wolffian body become continuous 
 with the rete testis, perhaps it may be desirable to call to mind 
 the anatomical arrangements at this particular moment. Both 
 in the ten weeks' embryo, and in one of twelve weeks (fig. 23), 
 there is, at the isthmus of the testicle, no line of demarcation 
 whatever between the parenchyma of the testicle and that of 
 the Wolffian body. The aggregation of spermatic cells which 
 constitutes the rete testis is in the stroma, and has no dis- 
 tinct limits (fig. 23). Moreover, the tubules of the sexual part 
 of the Wolffian body or vasa efferentia extend into the hilum of 
 the testis, and gradually lose their identity, owing to their cells 
 having become disseminated in the meshes of the stroma. But 
 those meshes are full of rounded unbranched seminal cells, so 
 that there is a continuity of cell elements between the rete testis 
 and vasa efferentia. As cell arrangement proceeds in the body 
 of the testicle, these intermediate cells form the last link in the 
 chain which unites the sexual tubules of the Wolffian body to 
 the rete testis. The actual arrangement of these indifferently 
 disposed intermediate elements does not begin in the human 
 embryo until about the sixth month of intrauterine life. The 
 accompanying drawing has been made from the testicle of a 
 human embryo at about the eighth month of intrauterine life 
 (fig. 35), and although it does not demonstrate an absolute 
 physical continuity of cell elements between tubules of 
 epididymis and those of the testicular lobules, yet, in my 
 opinion, such an union does exist. The elements are arranged 
 in irregular and crooked strings, so that no single section could 
 give adequate evidence upon this point. 
 
 This account of the process by which an egress is provided 
 for the seminiferous tubes is, allowing for differences in the 
 mode of expression, very like that which Janosik describes for 
 the rabbit and cat. However, the examination of testicles of 
 various animals^ — dog, cat, goat, and rabbit — inclines me to 
 
 E 
 
66 PROFESSOE C. B. LOCKWOOD. 
 
 believe that the process is not the same in every type, but that 
 the tubules of the Wolffian body may participate in different 
 animals to a varying extent in forming the rete testis. If this 
 surmise be correct, it would tend to explain the various and con- 
 tradictory accounts which may be read in the voluminous litera- 
 ture of the subject. Under these circumstances, it has been 
 deemed advisable to adhere to one type, and human embryos 
 seem as suitable as any others, and have, therefore, been used. 
 It is not proposed to follow the histological differentiation of the 
 tubules of the testicle and epididymis beyond the process of 
 establishment. But before leaving the subject, a word may be 
 spoken upon the fate of the glomeruli of the urinary portion of 
 the Wolffian body. These have been seen at the height of 
 their perfection in male human embryos of the tenth week 
 (fig. 25). At the twelfth week it was still quite easy to ascer- 
 tain their persistence ; but in the male none could be found 
 at the sixth month, nor at the eighth month. 
 
 But, in a specimen of the ovary and broad ligament of a child 
 eight months old, lent to me by Dr Walter Griffith, there were 
 structures near the hilum of the ovary which had the usual 
 characters of glomeruli, except that Wolffian tubules were not 
 traced to them. 
 
 It may be gathered from the foregoing that I have not been 
 able, either in rabbits' or human embryos, to confirm Balfour's 
 assertion that the glomeruli receive the testicular tubules. 
 
 We are now in a position to mark what becomes, in the male, 
 of the sexual and urinary portions of the Wolffian body. The 
 sexual tubules become the vasa efferentia, whilst the urinary 
 tubules may persist, and constitute the well-known organ of 
 Giraldes. Some of them may even grow, and persist as the 
 vasa aberrantia. These tubules, when present, vary in num- 
 ber, and one of our pupils, Mr Stanley, has dissected a testicle 
 for me, in which four can easily be made out. This is such 
 an unusual circumstance that I have made a sketch of the 
 specimen (fig. 86). 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. G7 
 
 LECTURE III. 
 
 Oviducts. 
 
 Before proceeding with the transition of the testicles, the 
 liistory of the ovidncts, or, as they are usually called, the 
 Mlillerian 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 con- 
 venient 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 
 mm. long, and nearly at the period of their greatest develop- 
 ment ; 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 pro- 
 minence 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 uro- 
 genital sinus. 
 
 The portions of the oviducts Avhich had developed were A, 
 their abdominal openings, and B, a short length of their epi- 
 thelial 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 
 
68 PROFESSOR C. B. LOCKWOOD. 
 
 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 situ- 
 ated 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, its 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 oviduct. 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 
 favour of the view of Egli, Kolliker, and Janosik, 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 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 69 
 
 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 pro- 
 nephros 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 sup- 
 posed 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 Kolliker'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 cir- 
 cumstance 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. 32), and which 
 was fths of an inch long, and estimated to have arrived at about 
 the seventh week of intrauterine life. In this specimen the 
 genital mass was in the indifferent stage, and towards its upper 
 end^ there were several villous projections, the commencement, 
 presumably, of the fimbriae 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 
 
 . ^ Entwickclungsgcscliiclite, p. 977. 
 
 ^ 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. 
 
70 PROFESSOR C. B. LOCKWOOD, 
 
 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 
 (fig. 39, p. 52). 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.^ 
 
 IVdnsition 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. 
 
 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 
 
 ^ Wertlieimer, art. "Testicule," Die. Encychpcdique des Sciences Medicalcs, 
 p. 533. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 71 
 
 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 pre- 
 liminary, be studied by means of rabbits' embryos. 
 
 The transition of the reproductive gland has two stages ; the 
 first comprises alterations in its position mthm the abdominal 
 cavity; the second its passage through the abdominal wall into 
 the scrotum. 
 
 Before discussing these two phases, it is desirable to endea- 
 vour 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 par- 
 ticularly to the pelvis, are likely to yield the safest infonnation 
 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 (p. 45, fig. 29, PI. II.), 
 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 for- 
 wards (tig. 30, PI. II.) until they lie behind the middle third 
 of the Wolffian body, and consequently opposite the genital 
 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 is 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, 
 
72 PROFESSOR C. B. LOCKWOOD, 
 
 and assuming that the latter were immobile, it would be easy 
 to imagine that movement had occurred. Another circum- 
 stance 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, p. 52), 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 rela- 
 tions 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 repro- 
 ductive 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 vertebrae. For instance, in the embryo of 
 thirteen and a half days, whose Wolffian body and genital 
 mass was described in the second lecture (p. 39, fig. 37), the 
 cartilaginous bodies of the vertebrae 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 
 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 (fig. 1, p. 3). 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 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 73 
 
 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 {i.e., the Wolffian body) may be supposed to have 
 imdergone. 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 
 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 
 
74 PROFESSOR C. B. LOCKWOOD. 
 
 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 suit- 
 able for showing each stage in the development of the per- 
 manent 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 develop- 
 ment 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 intra- 
 uterine life, has been mentioned in which the kidney lay behind 
 the genital mass and Wolffian body, much in the same way as 
 it did in the rabbit (fig. 31, PL II.). 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. 52 ; also fig. 34, PI. II,), the various features 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 75 
 
 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, it lies 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 develop- 
 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 
 
76 PROFESSOR C. B. LOCKWOOD. 
 
 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, PI. II.), 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 
 skeleton and the kidneys themselves have developed and grown 
 in its proximity. 
 
 Relation of the Mesonephros to the SuprarenaVBodies. 
 
 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 genir 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 77 
 
 tal masses, have altered their positions. In speaking of the 
 sections through the inner part of the Wolffian body of this 
 seven weeks' embryo (p. 62), it was said that " the fore- 
 most glomeruli, 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 sub- 
 sta,nce of that organ. Not only am I unable to discover any 
 line of demarcation between the glomerular part of the meso- 
 nephros 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 supra- 
 renal (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 a supporting stroma, which is directly continuous with that 
 of the Wolffian body, which, it may be rem-embered, has already 
 been depicted and described (PI. II., fig. 24, and also p. 36). 
 Towards the centre of the suprarenal body the radiate arrange- 
 ment of its elements ceases, and instead are loculi of cells more 
 loosely aggregated, and of larger size and oval. 
 
 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 
 
78 
 
 PROFESSOR C. B. LOCKWOOD. 
 
 the last can only be considered a minor and perhaps unimport- 
 ant point of resemblance. 
 
 Pancreas.... 
 
 Wolffian B.. 
 Ureter 
 
 ...Suprarenal 
 Body. 
 
 .Kidney. 
 
 Fig. 47. — Continuity of Wolffian and Suprarenal Bodies in a Human Embryo of 
 the seventh week. — (Electrotype from photograph of section.) ^ 
 
 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 (fig. 40, p. 56). 
 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. 
 
 In this embryo the kidneys lie opposite the lumbar spine, 
 and their position is the same as in the younger specimen 
 (fig. 40, p. 56). 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 
 
 ^ I am indebted to my friend Mr Cosens for the micro-photograph from which 
 this electrotype was made. 
 
THE DEVELOPMENT AND TEANSITION OF THE TESTIS. 79 
 
 tunica albuginea and tubuli seminiferi have appeared (fig. 41, 
 p. 57)) 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 remem- 
 bered 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 con- 
 tinuous with the peri-uretral glomerular tissue, nevertheless 
 there is little doubt but that such is the case. But, in addi- 
 tion, 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 
 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. 
 
 1 " On the Suprarenal Bodies of the Vertebrata," W. F. R. Weldon, Quart. 
 Jour. Micr. Sci., vol. xxv. p. 137, 1885. 
 
80 PROFESSOR C. B. LOCKWOOD. 
 
 Also JanoSik^ has found that the suprarenals develop in con- 
 nection 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 con- 
 duced. 
 
 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 im- 
 portant. 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 main- 
 tained the position which was determined for them by the 
 development in their proximity of the kidneys and pelvis. 
 
 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 
 
 ^ " Bemerkungen liber die Entwicklmig der Nebenniere," Arcliiv filr Micros. 
 ■Anatomic, Band xxii.,1883, p. 738 et seq. 
 
THE DEVELOPMENT AXD TRANSITION OF THE TESTIS, 81 
 
 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 (6) to changes in their 
 surroundings, including the kidneys. It is convenient to begin 
 with the last mentioned ; and, in the first place, it seems im- 
 probable 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. 56), 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 foi'mation of the last-named 
 structures. Now, it is significant to observe that whilst the spinal 
 column, especially of its lumbar part, is 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 
 
82 PROFESSOR C. B. LOCKWOOD. 
 
 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 is 
 possibly the case ; and I have already argued that the circum- 
 stance 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 either sex. 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, PI. IL), 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 on upward prolongation. So far as concerns 
 its relation to the pelvis, the sexual gland is almost in the 
 same position as it 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 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 83 
 
 ■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 ab 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. 3. Development and 
 growth of kidney behind mesonephros and genital eminence. 
 4. Development and growth of pelvis behind lower end of meso- 
 nephros. 5. Alterations in upper part of mesonephros; its 
 partial atrophy and probable incorporation in suprarenal cap- 
 sule. 6. Growth of lumbar spine. 
 
 If the observations recorded in the earlier part (p. 70) of this 
 Lecture be correct, the testicle has attained its position upon 
 the brim of the pelvis, and almost in contact with the hypo- 
 gastric arteries and the abdominal walls, by a gradual process 
 of development and growth. But already, at the third month, 
 preparations are being made for the active transition of the 
 gland through the abdominal wall, and its final deposition in 
 the scrotum. Amongst these preparations are comprised the 
 further development of the mesorchium and of its ascending and 
 descending processes, namely, the plica vascularis and the plica 
 gubernatrix, the development of the gubernaculum itself, the 
 development of the inguinal canal, and, finally, the development 
 of the scrotum. 
 
 It is convenient to refer briefly to such of these as can be 
 seen with the naked eye, and then proceed with those whicii 
 require to be studied by means of histological sections. 
 
84 PROFESSOR C. B. LOCKWOOD. 
 
 The Mesorchiuwi, Plica Guhernatrix, and Plica Vascularis. 
 
 The mesorchium has frequently been mentioned before, and 
 is the fold of peritoneum which unites the mesonephros, and 
 afterwards the epididymis, to the back of the abdomen ; the 
 word is not, perhaps, quite free from ambiguity, for the mesen- 
 tery belongs more especially to the mesonephros, but as the name 
 is established by custom, it is desirable to continue its use. At 
 the third month the mesorchium is but a slender support, and 
 is prolonged upwards from the epididymis in a small triangular 
 fold ; and, as this subsequently contains the spermatic vessels, I 
 have, in a paper on " Encysted and Infantile Hernia," ^ ventured 
 to call it the plica vascularis. Without doubt the plica vascu- 
 laris is the same as the fold which at an early age unites the 
 upper end of the Wolffian body to the diaphragm, and is 
 called by Kolliker'^ the diaphragmatic ligament of the meso- 
 nephros (Zwerchfellsband der Urniere). However, in the later 
 stages these relations of this fold are quite subordinate ; 
 whilst, as will be seen, its relations to the spermatic vessels 
 are of practical and pathological importance. The mesorchium 
 is shown in the accompanying drawing, made from a human 
 embryo of the third month, and in this specimen the testicle and 
 kidney are a little way apart, the separation being caused, I 
 believe, by the growth of the lumbar spine and pelvis, including 
 the sacrum in the pelvis. The plica vascularis does not reach 
 quite as far as the kidney, but is, nevertheless, an obvious feature 
 (PI, III, fig, 48). The lower part of the mesorchium is, on 
 either side, continued along the right and left genital strings, to 
 become continuous with a cord which passes down to the outer 
 side of the hypogastric arteries, and ends in the abdominal 
 wall. This cord is an early stage of the gubernaculum testis, 
 and the downward prolongation of the mesorchium^ is the 
 plica gubematrix. It is hardly requisite, perhaps, to trace 
 minutely the gradual growth of the mesorchium. It does not, 
 perhaps, develop luxuriantly in every foetus, but at about the 
 
 1 "The Morbid Anatomy and Pathology of Encysted and Infantile Hernia," 
 by C. B. Lockwood, Med. Chir. Trans., vol. Ixix., 1886. 
 ^ Kblliker, EntwicMungsgescMcMe, p. 959. 
 ^ The mesorchium is sometimes called " Seller's fold." 
 
THE DEVELOPMENT AND TEANSITION OF THE TESTIS. 
 
 85 
 
 end of the seventh month it usually has the appearance seen in 
 the accompanying sketch (fig. 49). The base of the mesorchium 
 was loosely fastened along the psoas muscle, and its free edge 
 ended upon the epididymis and testicle ; its lower fold contains 
 the gubernaculum, and the upper the spermatic vessels. How- 
 ever, at this age (seventh month) the chief interest of the upper 
 process centres in its relation, on the right side, to the caecum, 
 vermiform appendix, ilium, and mesentery, to which it is now 
 (towards the end of intrauterine life) adherent ; and later it will 
 be seen that this may have an important bearing upon the 
 pathology of congenital csecocele ; on the left side it passes 
 
 Fig. 49.^ — Drawing made from a seven or eight months' foetus to show the fold 
 (plica vascularis) which connects the testis with the csecum. T, testicles ; 
 E, epididymis ; P, psoas ; V, vas deferens : G, plica gubernatrix, disappear- 
 ing into processus vaginalis ; P. V, plica vascularis ; C, csecum ; S, spermatic 
 artery ; I, ilium. 
 
 upwards to the sigmoid flexure. The plica gubernatrix, more- 
 over, disappears below in a peritoneal pouch, which is the 
 beginning of the processus vaginalis. The formation of this 
 protrusion may be considered after the development of the 
 scrotum and inguinal canal. 
 
 The Development of the Scrotum and Inguinal Canal, includ- 
 ing the Ascending and Descending Crerniaster. 
 
 It is proposed as far as possible to pursue this branch of the 
 subject by means of histological sections. As far as can be 
 
 ^ I am indebted to the Council of the Royal Medico-Chirurgical Society for per- 
 mission to use this and another block. 
 
86 PROFESSOR C. B. LOCKWOOD. 
 
 ascertained, most of our knowledge of it has been learnt by 
 dissection ;^ yet, although a great deal of information has been 
 gained in this manner, nevertheless, the embryonic tissues are 
 so delicate and hard to manipulate that there seems to be still 
 r jom for further inquiry. This refers more particularly to the 
 histology of the earlier stages, and I now propose to describe 
 them as briefly as possible, using for the purpose human em- 
 bryos, which may be supposed to have attained the seventh, 
 tenth, twelfth, and twentieth weeks of intrauterine life. 
 
 At the seventh week the structure of the abdominal wall is 
 very rudimentary, and it contains but a trace of muscle in its 
 substance. Its exterior is covered with a layer of epiblast, 
 whilst it is lined within by a clearly defined but tenuous mem- 
 brane, which is the beginning of the peritoneum. Where the 
 peritoneum lines the front abdominal wall there is no trace of 
 subperitoneal areolar tissue, but towards the back and lower part 
 of the abdomen that tissue is abundant, even at this early age. 
 The main bulk of the abdominal wall is composed of ordinary 
 mesoblastic tissue of considerable density, but towards the 
 middle line a quantity of fine deeply stained fibres betoken the 
 advent of the rectus abdominis. The appearances in this 
 embryo seem to indicate that, so far as concerns the muscles of 
 the trunk, the degree of their development is determined by 
 their size more than by other considerations ; and, in con- 
 sequence, such muscles as the gluteus maximus, erector spinse, 
 and ilio-psoas are the furthest advanced. In this embryo, also, 
 the pubic cartilages were still some distance apart, and the 
 mesoblast of the abdominal wall continued over their surface 
 into the perinseum, making a decided bulge on either side 
 below" the pubes, in the situation of the future scrotum or labia 
 majora, as the case may be ; for it has been repeatedly said that 
 the genital mass of this embryo is in the indifferent stage. 
 The scrotal mesoblast is exactly the same as that which forms 
 the abdominal wall, with the exception that it cannot be said 
 with any degree of confidence that there is any indication of 
 the conversion of any part of it into muscle. 
 
 1 F. Bramann, in his " Beitrag zur Lehre von dem Descensus testiculorum und 
 dem Gubernaeulum Hunteri des Menschen," ArcJiiv filr Anat. und Entwick., 
 1884, p. 310 et seq., gives an exhaustive account of the literature of the subject, 
 and his investigations will be mentioned again. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 87 
 
 Before leaving this embryo, I may mention that the bladder 
 and hypogastric arteries are of some size, and are closely related 
 to the lower third of the wall of the abdomen, behind the 
 developing rectus abdominis ; their width, taken together, is 
 considerable, and they make the middle part of the lower front 
 wall of the abdomen look very solid and impervious. 
 
 In the human embryo of the tenth week of intrauterine life 
 (fig. 40, p. 56) the development of the abdominal walls has 
 made further progress. Not only the rectus abdominis, but also 
 the external oblique and transversalis, are clearly marked. The 
 fibres of the various muscles are imbedded in embryonic 
 connective tissue, which is most abundant beneath the cutan- 
 eous surface and almost absent where the peritoneum lines the 
 transversalis and rectus muscles. The sections which divide the 
 abdominal wall near the site of the future internal abdominal 
 ring show that preparations have commenced which may be 
 supposed to be capable of facilitating the transition of the 
 testicle into the scrotum. Before proceeding to detail them, 
 it may be desirable to indicate the point at which they are seen. 
 As regards the cartilaginous skeleton, it is situated almost 
 vertically above the outer margin of the thyroid foramen, and 
 consequently just internal to the head of the femur. In the 
 next place they are immediately above the inner side of the 
 external iliac vein, which is very large, and external to the 
 hjrpogastric arteries. As in the younger embryo, these vessels, 
 together with the bladder, occupy a large part of the lower 
 middle part of the abdominal wall. Therefore I am about to 
 describe the abdominal wall at the point at which the internal 
 abdominal ring afterwards appears. The abdominal wall has 
 the following layers : — externally, of course, a cutaneous cover- 
 ing, which has beneath it a thick layer of undifferentiated meso- 
 blastic tissue ; next comes a thin and deeply staining lamella 
 which merges above in muscular fibres, and, I take it, represents 
 the external oblique ; a third muscular layer forms the next 
 stratum, and upon its inner surface the peritoneum is closely 
 applied, except at a point which will be mentioned directly; 
 the last muscular layer constitutes without doubt the internal 
 oblique and transversalis. Of these various strata, the cutaneous 
 one may be dismissed without further comment. The sub- 
 
88 PROFESSOR C. B. LOCKWOOD. 
 
 cutaneous mesoblastic tissue, as in the younger embryo, extends 
 over the pubes and is continuous with the scrotal eminence. 
 Towards the inner side of the iliac vein, and in the position of 
 the internal abdominal ring, the external oblique layer makes a 
 decided bend into the subcutaneous mesoblastic tissue and 
 towards the scrotum. The concavity of this projection, which, 
 I believe, is an early stage of the external spermatic fascia, is 
 thinly lined with a layer of muscular fibres derived from the 
 succeeding layer ; these represent the beginning of the descend- 
 ing portion of the cremaster muscle, and their hollow is filled 
 with embryonic connective tissue. Presently, ascending cre- 
 masteric fibres will be mentioned, which are derived from the 
 muscular fibres of the abdominal wall which are nearest to the 
 peritoneum and which ascend with the gubemaculum testis. 
 
 In this embryo, moreover, the inguinal canal has begun. 
 The muscular layer of the lower abdominal wall {i.e., of the 
 internal oblique and transversalis) may be said to have below 
 three portions, namely, the descending cremasteric fibres, the 
 ascending cremasteric fibres, and a middle set which descend no 
 farther than the point at which the previous two are given off. 
 In consequence, an interval is left in the situation of the in- 
 guinal canal which has the ascending and descending cremaster 
 for its front and back boundaries, and the middle fibres for its 
 roof The contents of this rudimentary inguinal canal are a 
 quantity of embryonic connective tissue, and some gubernacular 
 fibres which will be mentioned directly. 
 
 The peritoneum has been said to be closely united to the 
 inner surface of the transversalis muscle, and I have now to add 
 that it has nothing which corresponds to the bulging of the 
 external spermatic fascia and cremaster. Its surface is quite 
 even, with the exception of a short process which runs upwards 
 from the abdominal wall to either genital string, and which is 
 the beginning of the plica gubernatrix. There is a leash of 
 fibres within the plica like those of areolar tissue, and these 
 fibres pass upwards to the genital string and to the peritoneum ; 
 below they spread out and pass beneath the edge of the mus- 
 cular layer of the abdominal wall (internal oblique and 
 transversalis), and mingle with the walls of the projection formed 
 by the external spermatic fascia and cremaster. The muscular 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 89 
 
 fibres of the abdominal wall, which are nearest the peritoneum, 
 instead of terminating, as the others did, to form an inguinal 
 canal, are, as I have already said, continued into the base of the 
 plica gubernatrix, and will be mentioned again in speaking of 
 the structure of the gubernaculum testis. 
 
 Finally, the testicle itself lies upon the ilium, and a very little 
 way from the front abdominal wall. The peritoneum in the 
 neighbourhood of the testicles and of the back wall of the 
 abdomen has beneath it an abundance of loose embryonic 
 connective tissue. 
 
 Assuming that these observations and inferences are correct, 
 it is clear that the scrotum, and some of its layers, is formed 
 long before the transition of the testicle, and quite inde- 
 pendently of that event. There is nothing new or novel in 
 this, but it is interesting to record the earliest stages of the 
 process. Carus's theory, that the testicle, in its descent, carried 
 down its own investments from the abdominal wall, has been so 
 abundantly falsified that it is quite unnecessary to argue that 
 the foregoing is also antagonistic to the views of that authority.-"^ 
 This is a convenient point to mention that the hypogastric 
 arteries seem to have an influence in determining the point in 
 the abdominal wall at which the processus vaginalis begins to 
 appear. It has been stated in an earlier part of this lecture 
 that those vessels, together with the bladder, render the lower 
 median part of the abdominal wall exceedingly thick and 
 impervious ; whilst the lower and external part is compara- 
 tively weak and unprotected. From this it follows that after 
 the testicle and vas deferens have passed into the scrotum the 
 ostium of the processus has the hypogastric artery upon its inner 
 side, and it is only after that vessel has dwindled that the epi- 
 gastric artery takes its place, and becomes the inner boundary 
 of the ostium. Moreover, at first the vas deferens in its course 
 to the migrated testicle turns round the hypogastric artery, and 
 receives a small branch from it — the deferential artery. 
 
 The next embryo, that of the twelfth week, was, of course, much 
 larger and better developed than that which has just been de- 
 scribed. It was cut into a series of transverse sections, which con- 
 
 ^ Sappey, Traits d'Anatomie Descriptive, vol. iv. p. 581, 1874, adduces 
 several cogent reasons against Carus's theorj'. 
 
90 PROFESSOR C. B. LOCKWOOD. 
 
 firmed the inferences drawn from the previous embryo, which, it 
 may be remembered, was cut longitudinally. The testicle of this 
 twelve-weeks' embryo has already been figured (fig. 33, PL II.), 
 and lay upon the brim of the pelvis and very close to the abdomi- 
 nal wall and hypogastric arteries. The genital strings, right and 
 left, were united to thelower part of the abdominal wall by the plica 
 gubernatrix. This fold was narrower at either end than in its 
 middle part, where it bulged somewhat. Its substance con- 
 sisted of round and spindle-shaped cells ; the latter had a 
 decided likeness to unstriped-muscle cells, and were continued 
 into the substance of the abdominal wall, in the situation of the 
 inguinal canal. Moreover, the muscular fibres, which have been 
 called the ascending cremaster, entered the base of the plica 
 gubernatrix, and were, without question, continued upwards 
 beneath the peritoneum, which formed the plica, as far as the 
 genital string, or, as it might now be called, the vas deferens. 
 At the point at which the plica gubernatrix was continuous with 
 the peritoneum of the abdominal wall there was no irregularity 
 or trace of the processus vaginalis. Both the external spermatic 
 fascia and the descending cremaster bulge towards the scrotum, 
 which consisted of embryonic connective tissue, whose stellate 
 cells were very clear and unmistakable, and without any admix- 
 ture of muscular fibres except those which have just been 
 mentioned. The two halves of the scrotum had almost united, 
 although in the perineum there was still a wide opening 
 beween the urethra and the exterior. 
 
 The main difference, therefore, between this embryo of the 
 twelfth week and that of the tenth, assuming that their ages 
 have been rightly calculated, seems to consist in a greater 
 development of the muscular constituents of the gubernaculum 
 testis, and of a further fusion of the halves of the scrotum. 
 
 It has been said that the testicle of this twelve weeks' 
 embryo was upon the brim of the pelvis and, quite close to the 
 abdominal wall, and this position, it will be perceived, is the 
 same as that which the Wolffian body and genital mass or 
 testicle occupied in embryos of the seventh and tenth weeks ; 
 moreover, it may be added that, allowing for the growth of 
 surroundings, its position in relation to the acetabular portion 
 of the pelvis is practically the same. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 91 
 
 The next stage, in which the development of the scrotum, and 
 of the coverings of the testicle, and of the inguinal canal were 
 investigated by means of histological sections, was probably the 
 fifth month. In this case the processus vaginalis and guber- 
 naculum testis had, as will be presently described, definitely 
 appeared ; but, before mentioning them, the scrotum and in- 
 guinal canal may be referred to. Perhaps it is to be regretted 
 that there is such an interval between this and the previous 
 embryos, but as development proceeds it becomes more and 
 more difficult to obtain a reliable series of histological sections, 
 and practically it will be found that the hiatus is not likely to 
 lead to erroneous conclusions. 
 
 The foetus from which the following conclusions were drawn 
 was in all respects well formed, and had probably attained the 
 fifth month of intrauterine life ; its fingers and toes had fairly 
 well-developed nails. Of course the sex was quite unmistakable, 
 and the penis and scrotum were, so far as regards their naked- 
 eye characters, clearly and definitely established. A series of 
 longitudinal sections of the pelvic region, and of the abdomen 
 below the umbilical cord, were prepared by the paraffin method, 
 after the bones had been decalcified. In this, as in nearly all 
 the other specimens, the stain used was picro-carmine. 
 
 The testicles lay in contact with the abdominal wall, just 
 external to the hypogastric arteries, and apparently in front of 
 the acetabular portion of the pelvis. But at this stage it is 
 harder to determine this point, because, owing to the growth of 
 the muscles and other tissues, the gland is separated some 
 distance from any bony landmark. Moreover, the testicle has 
 grown so little in comparison with its surroundings, that it 
 has become quite subordinate. 
 
 As may have been inferred, the testicle is separated from the 
 kidney by an interval of more than a quarter of an inch. It 
 would be easy to imagine that this separation might be due 
 to an actual locomotion of the testicle itself, but the fore- 
 going observations show, I think, that the gland and its 
 epididymis have still the same relation to the pelvis as their 
 precursors, the Wolffian body and genital mass, had. The 
 various parts of the pelvis, ilium, ischium, pubes, and sacrum 
 have grown enormously, and also the lumbar spine. Indeed 
 
92 PROFESSOE C. B. LOCKWOOD, 
 
 the latter has grown so much that the spinal medulla only 
 reaches as far as a point which may be judged to be the 
 junction of the sacrum with the lumbar spine. 
 
 However, in this foetus the preparations for the actual transition 
 of the testicle through the abdominal wall have made consider- 
 able progress, and, as we shall see, the processus vaginalis and 
 gubernaculum testis are definitely established. But before these 
 are described, the structure of the scrotum may be mentioned. 
 
 The surface of the scrotum was covered with a layer of 
 epithelium exceedingly like that which covers the cornea, and 
 this likeness was heightened by the absence of papillae. In 
 other regions the deeper layers of the epidermis were decidedly 
 irregular, and rudimentary papillae could be discerned. Beneath 
 the epidermis there was a dense layer of spindle-shaped nucleated 
 cells, the unstriped muscle fibre cells of the dartos. The bulk 
 of the scrotum consisted of ordinary embryonic connective tissue, 
 but its irregular cells looked more fibrillar than in the embryo 
 of twelve weeks. Imbedded in this tissue was a denser layer of 
 fibres, prolonged downwards from the external oblique muscle ; 
 these looped towards the perinseum, where they became gradu- 
 ally fainter, and finally disappeared. This layer, it may be 
 assumed, was a further stage of the external spermatic fascia. 
 The superficial part of the muscular layer of the abdominal 
 wall also sent numerous fibres into the scrotum, where they 
 spread out, and seemed to terminate ; these are the fibres 
 which have been called the descending cremaster. In the 
 vicinity of the pubic cartilage the muscular fibres made smaller 
 loops, and are attached to that part of the skeleton. 
 
 It may be mentioned that as yet the fibres of the various 
 skeletal muscles, although well developed, had no appearance 
 of striation ; except perhaps in the case of the gluteus maximus 
 and other large muscles, in which it was in places faintly 
 indicated, but of course the mode of preparation may have 
 made the striations indistinct. The internal spermatic fascia 
 is a covering of the testicle which has not been mentioned. 
 But it is questionable whether the transversalis fascia, of which 
 the tunic in question is a part, is itself definitely formed. As 
 in the case of the younger embryos, the peritoneum is closely 
 applied to the transversalis muscle, although there is, even in 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 93 
 
 this position, a small quantity of tissue suitable for conversion 
 into a fascial layer. However, even this can hardly be discerned 
 in the neighbourhood of the processus vaginalis. 
 
 There is a striking difference in the amount of subperitoneal 
 tissue at the front and back of the abdomen. As I have just 
 said, there is hardly any in front, whilst behind it is exceedingly 
 abundant, and loose in texture. 
 
 It is hardly necessary to point out that in almost every 
 particular the histology of this five months' embryo confirms 
 and extends the conclusions drawn from those of the tenth and 
 twelfth weeks. Nor is it necessary to add that the external 
 spermatic fascia and the descending cremaster seem to have 
 reached the scrotum by some process of growth and develop- 
 ment, and not by any manner of traction. 
 
 Processus vaginalis. 
 
 It is so well known that a peritoneal pouch precedes the 
 testicle into the scrotum, that without further premise, we may 
 proceed to discuss the manner of its formation. Presently it 
 will be seen that the processus vaginalis has attained a fair 
 degree of development in the five months' foetus which has just 
 been described, and without doubt it appears a little earlier in 
 intrauterine life. Care has been taken to point out that there 
 was no trace of it in the series of sections made from either the 
 ten weeks' embryo or that of twelve. Unfortunately, I have 
 been unsuccessful in preparing histological specimens from 
 embryos of between the twelfth and twentieth weeks of intra- 
 uterine life. But in dissected specimens of embryos of an inter- 
 mediate size and development, and which might be assumed to 
 have reached the sixteenth week of intrauterine life, there was 
 a dimple in the peritoneum at the lower end of the plica 
 gubernatrix, and this doubtless was the early stage of the 
 processus. This accords with Bramann's^ observations, but 
 Kolliker^ says the processus begins at the third month, and 
 Weil ^ at the end of the second. 
 
 Reverting to the foetus of the fifth month, I would direct 
 
 ^ Ibid., p. 320. ^ Entwicklungsgeschichte, p. 994. 
 
 ^ Weil, " Ueber den descensus testicnlorum," &c., Zeitsclirift fiir Heilkunde, 
 Bd. v., Prag. 1884, p. 226 et seq. See also footnote, p. 102, 
 
94 
 
 PROFESSOR C. B. LOCKWOOD. 
 
 attention, first of all, to the processus vaginalis at its opening into 
 the abdomen. The first section which has been drawn (PI. III. 
 fig. 50) shows very clearly the lumen of the processus vaginalis 
 and its relation to the abdominal wall. In front of it are fibres 
 of the internal oblique and transversalis and of the external 
 oblique muscles. The abdominal opening has not been divided 
 at its widest part, and in sections a little farther from the 
 middle line the projecting lips seen in the drawing are absent, 
 
 Fig. si.-' — Processus vaginalis in transverse section. T, testicle; LA, iliac 
 vessel ; P.G., plica gubernatrix and gubernaculum ; P.V., processus vaginalis ; 
 Int. and T, internal oblique and transversalis ; E. 0, external oblique. 
 
 and the aperture involves not less than half the circumference 
 of the canal. The plica gubernatrix projects from the floor of 
 the processus and half fills its lumen ; traced upwards it passes 
 through the ostium and unites with the epididymis, but before 
 doing so receives muscular fibres, the ascending cremaster, from 
 the innermost layer of the abdominal muscles. The testicle lies 
 quite close to the ostium of the processus vaginalis, and is at 
 
 ^ I am indebted to the managers of the British Medical Journal for the use of 
 this and other blocks. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 95 
 
 least twice the size of that aperture. If next the lumen of the 
 processus vaginalis be traced in its course through the abdominal 
 walls it is found to diminish gradually (fig. 51), and end in the 
 midst of the muscular fibres of the internal oblique and trans- 
 versalis. The plica gubernatrix also dwindles in its downward 
 course, and ceases to project into the lumen of the canal. From 
 these appearances it may be inferred that at the fifth month the 
 processus vaginalis is a funnel-shaped canal, wide above and 
 pointed below ; moreover, they do not favour the supposition 
 that it has been produced by a force acting from within the 
 abdomen, but rather by traction applied to its pointed extremity. 
 In older foetuses, such as those of the sixth, seventh, and 
 eighth months of intrauterine life, the gradual progression of 
 the processus vaginalis into the scrotum can be traced by 
 dissection, and the mechanism of the process has been fully 
 described by numerous distinguished observers. It is sufficient 
 for the present to say that it always precedes the testicle 
 towards the scrotum, and it must be admitted that, as it nears 
 its completion, it ceases to possess a pointed extremity, and even 
 becomes more capacious towards its lower part. As we proceed 
 arguments will be advanced to show that, after its muscular 
 structure has become definitely established, the gubernaculum 
 is capable of exerting a certain degree of traction upon the 
 structures to which it is attached. The processus vaginalis is 
 one of these structures, and the weight of evidence seems to 
 favour the theory which attributes its production to the action 
 of the gubernaculum. Perhaps it is unnecessary in the be- 
 ginning to imagine an active contractive effort, and it may be 
 urged that, at the time the processus vaginalis appears, the 
 gubernaculum is structurally incapable of contraction. It is 
 difficult to say at what moment tissues become capable of 
 contraction. The heart beats before its walls show traces of 
 conversion into muscle, and therefore the above is at least a 
 doubtful argument. But when the phenomena of the infantile 
 hernia and of congenital csecocele are considered, it will, I 
 think, be evident that the gubernaculum has great capabilities 
 of moving the peritoneum, and can also produce from it hernial 
 sacs — sacs in every way analogous to the processus vaginalis. 
 This question, together with an account of the relations which 
 
96 PEOFESSOR C. B. LOCKWOOD. 
 
 the processus vaginalis ultimately acquires to the testicle, the 
 vas deferens, the spermatic vessels, and also to the gubernaculum 
 and cremaster, may be conveniently deferred for a while. 
 
 The Transition of Sub-peritoneal Fat and Lipoma of the 
 Spermatic Cord. 
 
 It is of interest to remark that the processus vaginalis is 
 accompanied towards the scrotum by a quantity of sub-peritoneal 
 tissue and fat. In two full-grown foetuses which I have 
 examined, the fatty prolongation was very obvious, and in one 
 caused a slight projection at the external abdominal ring. The 
 sub-peritoneal fat of the foetus is quite unmistakable, and dis- 
 posed in small greyish lobules, quite unlike the fine granular fat 
 of other regions. The import of this observation is that there is 
 every reason to believe that the fat which migrates into the 
 scrotum is the source of lipomata of the spermatic cord. Speci- 
 mens of this rather common affection ^ which I have dissected 
 are in the museum of St Bartholomew's Hospital,^ and they 
 show that the tumour is in intimate relation with the spermatic 
 vessels, and therefore in the position which sub-peritoneal fat 
 might be expected to occupy. In these cases the lobes of fat 
 were not continuous with that inside the abdomen, but, as Mr 
 Hutchinson shows, this circumstance has been observed in cases 
 of the same description. 
 
 The Ouhernaculum Testis. 
 
 This structure has already been mentioned several times, and 
 the first trace of it was noted in the histological sections of the 
 human embryo of the tenth week of intrauterine life ; and at the 
 twelfth week it could easily be seen with the naked eye. Few 
 things have given rise to so much controversy, and those who 
 are interested in the matter will find the views of the various 
 authorities, both ancient and modern, summarized in the 
 
 ^ For cases of tlie same sort see Curling, On the Testicle, p. 556 ; also Path. 
 Trans., vol. xxxvii., 1886, shown by Mr C. Stonham ; also a paper by Mr J. 
 Hutchinson, jun., p. 451 of the same volume, in which the subject is fully dis- 
 cussed. 
 
 2 Sp. 2812a. 
 
THE DEVELOPMENT AND TEANSITION OF THE TESTIS, 97 
 
 memoirs of Cleland/ Godard,^ Bramann,^ in the joint memoir of 
 Debierre and Pravaz,^ and elsewhere.^ 
 
 It would not, I think, serve any useful purpose to recapitulate 
 the literary researches of these authors, and in what follows it 
 is proposed to lay stress upon points which seem more particu- 
 larly worthy of notice, and which have not had the attention 
 they may be thought to deserve. 
 
 At the third month a distinction can hardly be drawn between 
 the plica gubernatrix and its contents, the gubernaculum. The 
 two together are a delicate band about i^gth inch long, con- 
 tinuous below with the abdominal wall, a little external to the 
 hypogastric arteries, and attached above to the genital string 
 (PL III. fig. 48), right or left, as the case may be. A proper 
 appreciation of the early upper attachment of the gubernaculum is 
 of some importance, because, as Bramann ^ says, authors are not 
 very explicit in their statements concerning it.'^ For instance, 
 if, as some would have us to suppose, it were thought that 
 the gubernaculum was, from the beginning, inserted into the 
 lower end of the Wolffian body or testicle, a difficulty would 
 arise as soon as an attempt was made to trace corresponding 
 parts in the male or female. Every one would admit that the 
 round ligament of the uterus is analogous to the gubernaculum 
 testis, and yet the round ligament does not accord with current 
 descriptions of the gubernaculum, inasmuch as it is attached 
 neither to the parovarium nor to the ovary itself, but to the 
 uterus. The cause of the dilemma and its explanation are 
 alike obvious, if the earliest insertion of the gubernaculum into 
 the genital string be recognised ; later, it will be seen that in 
 the male the gubernaculum acquires, during the 3rd, 4th, 5th, 
 and 6th months, attachments to the epididymis, to the testicle, 
 
 ^ Mechanism of GtCbernaculum Testis, 1856. 
 
 2 M. E. Godard, "Etudes sur la Menorcliidie et la Cryptorchidie chez I'liomme," 
 Comptes Rendus de la Soc. de Biologic, Paris, 1857, p. 315 et seq. 
 
 ^ Bramann, Archiv/iir Anat, und Fhys., 1884, p. 310 et seq. 
 
 ^ Ch. Debierre et J. Pravaz, Contribution a 1' etude du Muscle Cremaster, du 
 Gubernaculum Testis et de la Migration Testiculaire, Lyon AUdical, 1886, p. 
 101 et seq. 
 
 ^ Tourneaux et Herrmann, Dictionnaire Ency. des Sciences Medicales, 1886, 
 p. 525 et seq. ; and Weil, quoted before. ^ Ibid., p. 320. 
 
 '' Quain's Anatomy, 9th ed., vol. ii. p. 898 ; also fig. 805 ; also Heule, Hand- 
 huch der Eingfiweidelhere des Menschen, 1886, p. 340, fig. 255. 
 
 G 
 
98 PEOFESSOR C. B. LOCKWOOD, 
 
 and to the peritoneum of the back of the abdomen. As it 
 acquires these new attachments it comes to lie behind the vas 
 deferens, which, as Bramann points out, crosses over its upper- 
 most part. 
 
 A correct appreciation of the way in which the gubemaculum 
 attaches itself first to the vas, then to the vas and epididymis, 
 and afterwards to the testicle as well, explains several anomalies. 
 For instance, it occasionally happens that whilst the testicle and 
 epididymis is retained within the abdomen by adhesions or 
 other, causes, nothing but the vas deferens, together with a pro- 
 cessus vaginalis, reach the scrotum.^ Or, as Cloquet,^ Curling, 
 Follin, and Godard have shown, the vas and epididymis may 
 proceed towards the scrotum, whilst the body of the testicle 
 remains within the abdomen. A specimen in Guy's Hos- 
 pital Museum 3 illustrates this fairly well. My note of the 
 specimen says, that on the right side the testicle is within the 
 scrotum, but that the tunica vaginalis is patent, forming the 
 sac of a congenital hernia. On the left side the testicle is 
 undescended, and just within the internal ring. The epididymis 
 is apparently pulled away from the testis, and lies within the 
 neck of a process of peritoneum which occupies the inguinal canal. 
 The peritoneum in the vicinity of the testicle is drawn into 
 folds and pleats as if by dragging. The account which has been 
 given of the superior attachments of the gubernaculum would 
 explain these anomalies if two assumptions be allowed: first, 
 that the upper attachments of the gubernaculum sometimes 
 fail to develop properly ; and, secondly, that the gubernaculum 
 is capable of dragging the testicle through the abdominal wall, 
 and finally depositing it in the scrotum, or elsewhere. With 
 regard to the first point, I think it will be allowed that if it can 
 be shown that the upper end of the gubernaculum may have no 
 attachment at all, either to the vas deferens, the epididymis, or 
 to the testicle, it will be admitted that they may be sometimes 
 deficient in a less degree. In a very large and full-term 
 anencephalic monster, the scrotum had exactly the appearance 
 
 1 There is a specimen which illustrates this in the museum of tTniversity 
 College, Sp. 1137. 
 
 ^ Cloquet, Rccherchcs Anatomiqiies sur les Her'nies de V Abdomen, Paris, 1817, 
 p. 23 a seq. 3 Sp. 233930. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS, 
 
 99 
 
 which it presents in cryptorchids, very small and curiously 
 pinched together. When the abdomen was opened there was 
 only a trace of a processus vaginalis on either side, but the 
 gubernaculum was large and well developed. On the left side, 
 however, the gubernaculum, instead of having its ordinary con- 
 nections, spread out in a thin and wide leash of fibres, containe d 
 within a fold of peritoneum (fig. 52). On the right side of 
 
 SAscF 
 
 Fig. 52. — T, testicle; Ep., epididymis; SA and V, spermatic arteiy and 
 Tein ; F.d., vas deferens ; G.T., gubernaculum testis. 
 
 the body the attachments of the gubernaculum seemed to be 
 normal.^ It is also not without interest to note the condition 
 of the scrotum ; it looks as though the testicles had sent word 
 to say they were not coming, and, in consequeuce, it had not 
 developed. Perhaps I may mention here an embryo between 
 the 3rd and 4th months,^ in which, had it arrived at maturity, 
 the state of affairs would have been exactly the reverse. In 
 
 ^ This specimen is in the museum of St Bartholomew's Hospital, No. 3607a. 
 2 Also in the museum of St Bartholomew's Hospital, Sp. 3670Z). 
 
100 PROFESSOR C. B. LOCKWOOD. 
 
 this specimen the testicles and gubernacula seemed as well de- 
 veloped as they usually are at that age, but no trace of a penis 
 or scrotum or anus could be found, although there were one or 
 two indistinct pores in the perinseum. Obviously, in this case, 
 the testicles could never have accomplished their transition. 
 
 The second assumption, that the gubemaculuni is capable 
 of traction, has been maintained by some authors and denied 
 by others. Up to this point the present inquiry has favoured 
 the views of Cleland,^ Sappey,^ and Kolliker,^ who seem to 
 believe that in the transition of the testicle the gubernaculum 
 is passive, but that, whilst the testes themselves do not move, 
 their surroundings grow, and, at the same time, the guber- 
 naculum shortens but does not retract — a process analogous 
 to those which produce the relations of the spine and its 
 contents. However, these hypotheses fail to account for certain 
 interesting phenomena which sometimes attend the transition 
 of the testes. The muscular structure of the gubernaculum is, 
 I think, unquestionable, and it seems irrational to deny its 
 tissues the exercise of their function, namely, that of contraction. 
 Moreover, in a moment we shall see that the lower muscular 
 fibres of the gubernaculum are found to be attached — in addition 
 to the pubes, root of penis, and scrotum — in the perinseum and 
 in Scarpa's triangle. Is it not significant that the testicle 
 sometimes migrates into either of the last-named regions ? 
 Sometimes it lies close to the anus; in case mentioned in 
 the Lancet^ it was two centimetres from that orifice and 
 immovably fixed, and presently other instances will be forth- 
 coming. Now it seems hard to conceive how the testicle could 
 have arrived in this position by any process of growth and 
 development. Moreover, during the last stages of the transition, 
 the pyriform portion of the gubernaculum shortens. In a 
 foetus, 12 inches long, from crown to sole of foot (the legs 
 outstretched), and which had a mesorchium and gubernaculum 
 the same as that figured in an earlier part of this lecture 
 (fig. 49), the plica gubernatrix and the portion of the 
 
 ^ Cleland, Mechanism of the Gubernaculum Testis, Edinburgh, 1856, 
 ^ Sappey, Traiti d'Anatomie Descriptive, vol. iv. p. 581. 
 3 Kblliker, Entwieklungsgeschichte, p. 997. 
 * Baudry, Lancet, Sept. 1882, p. 454. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 101 
 
 gubernaculum between its layers measured -| inch long ; 
 whilst in a fully-developed foetus, 15^ inches long, and in 
 which the testicle was descended and the processus vaginalis 
 capacious, on looking within that pouch there was no plica 
 gubernatrix or trace of the part of the gubernaculum which 
 lies within that fold of serous membrane. Perhaps these 
 fcBtuses place the matter in too favourable a light, and there- 
 fore a few more measurements ought to be tabulated. It 
 seems as though the pyriform portion of the gubernaculum 
 does not bear a very constant proportion to the size of the 
 foetus. It was always measured from within the peritoneum 
 and as it lay in the plica gubernatrix ; the extra-peritoneal 
 portion, that which spreads out to the pubes, scrotum, and 
 perinseum, could not always, for obvious reasons, be measured. 
 
 No. 
 
 Size of Foetus. 
 
 Position of Testis. 
 
 Length of Gubernaculum. 
 
 1 
 
 7 in. 
 
 Within abdomen. 
 
 Pyriform^Vin. ; leash ^ in. 
 
 2 
 
 8^ in. 
 
 Within abdomen. 
 
 Pyriform f|r in. 
 
 3 
 
 8^ in. 
 
 Within abdomen. 
 
 Pyriform ^V in- 5 leash. 
 ^ ends on tuber ischii. 
 
 4 
 
 12 in. 
 
 Within abdomen. 
 
 Pyriform -^^ i^- 
 
 5 
 
 1^ in. 
 
 Fully descended. 
 
 None. 
 
 8 
 
 16 in. 
 
 On crest of pubes ; pro- 
 cessus ^ in. further. 
 
 Pyriform j^,- in. 
 
 7 
 
 17h in. 
 
 Bottom of scrotum. 
 
 Barely ^ in. 
 
 8 
 
 19 in. 
 
 Bottom of scrotum. 
 
 t\ in. 
 
 For the present, instead of pursuing this line of argument 
 any further, the lower attachments of the gubernaculum 
 may be mentioned. This branch of the subject has been 
 rendered clear and familiar by the writings of Curling,i and 
 therefore a brief description will suffice. Since, however, 
 that author based his observations mainly upon dissected 
 specimens, it is proposed, where necessary, to mention the 
 appearances seen in histological sections, prepared as usual 
 by the paraffin method. At the third month of intrauterine 
 life, the lower end of the gubernaculum looks to the naked 
 eye as if it ended at the peritoneum; but, as we have seen, 
 its tissues can be followed in the histological sections into the 
 
 1 T. B. Curling, A Practical Treatise on the Diseases of the Testicles, 4th 
 ed., 1878, p. 17 ct seq. 
 
102 PROFESSOR C. B, LOCKWOOD. 
 
 substance of the abdominal wall. Here they enter the hollow 
 of the descending cremaster and external spermatic fascia, 
 interlacing and interpenetrating the fibres. At this age, 
 moreover, the gubernaculum consists of two sorts of tissues. 
 Its main bulk is made up of round and spindle-shaped cells, each 
 with a deeply-stained, round or oval nucleus. Many of the 
 elongated cells seem to run from the abdominal wall towards 
 the genital string, and they have a decided likeness to un- 
 striped muscular tissue, and, as that substance is afterwards 
 found in abundance in the place they occupy, it is probable 
 that they are of that nature. The other tissue of which the 
 gubernaculum is composed is that which I have previously 
 spoken of as the ascending cremaster. This consists of a few 
 of the innermost muscular fibres of the abdominal wall, which 
 runs a short distance along the gubernaculum, lying imme- 
 diately beneath its peritoneal investment. At the third month 
 their presence can just be recognised, at the fifth they are no 
 longer doubtful, and at the seventh or eighth are abundant and 
 distinctly striated. These ascending fibres have been recognised 
 from the time of John Hunter, and since then most authors 
 have acknowledged their existence.^ They are better marked 
 in some animals than in man; for instance, in the hedgehog they 
 are very easily seen, and Hunter seems to have derived his 
 ideas from that animal. Their presence is also clearly shown in 
 various series of histological sections of rabbits' embryos, ranging 
 from the 15th to the I7th day after impregnation. 2 
 
 ^ Observations on Certain Parts of the Animal Oeconomy, by John Hunter, 1786. 
 
 ^ Quite recently (Jan. 1888), Dr Klein has kindly sent me a memoir by Pro- 
 fessor Weil ("Ueber den Descensus Testiculoram nebst Bemerkungen ueber die 
 Entwickelung der Scheidenheute und des Scrotums," Zeitschrift fiir HeilTcivnde, 
 Bd. v., 1884, p. 225 et seq.). In this memoir a full historical resume is given of 
 the gubernaculum and processus vaginalis. Moreover, the subject is studied 
 by means of histological sections, and it is not without interest to compare 
 the results with those which I have from an independent standpoint given. 
 This author (p. 248) describes and depicts the gubernaculum and processus as 
 being clearly established at the end of the second month. As regards the pro- 
 cessus this seems too early, and, judging from his sketch, the embryo in which 
 the appearances were seen was as old, or even older than, those which I have 
 considered to have been of the third month. However, the determination of the 
 age of embryos is always a doubtful point. Weil recognises in the gubernaculum 
 both spindle-shaped cells and striped fibres, together with some blood-vessels, 
 which arise from the spermatic and epigastric arteries (p. 254). 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 103 
 
 The gubernaculum grows rapidly after the third month, and 
 the part of it immediately below the testicle assumes a bulbous 
 shape, and, when quite fresh, looks dense and greyish- white. 
 Below this bulbous part its lower end spreads out in a leash of 
 unstriped muscle fibres, which seem both to blend with and 
 pierce the abdominal wall, and which can be seen quite plainly 
 by dissection. At about the fifth month these fibres spread out 
 fan-like in their main directions, namely, into Scarpa's triangle, 
 upon the pubes and root of penis, and towards the scrotum 
 (PI. III. fig. 53). By the sixth month, in a foetus which 
 measured 8| inches long with its legs extended, a thick fasci- 
 culus passed onwards into the perinseum, where it ended in the 
 tissues about the anus and over the tuber ischii. In larger 
 foetuses the perinseal band of the gubernaculum is oftentimes 
 better developed. In speaking of either the perinseal prolonga- 
 tion of the gubernaculum or that into Scarpa's triangle, which 
 from its position and direction may be called its saphenous pro- 
 longation, it is necessary to use guarded language, for although 
 they are both met with very frequently, yet their presence 
 cannot always be affirmed. However, it is difficult to trace 
 fibres of this description amongst foetal tissues, and at some 
 period before the end of fcetal life the perinseal band would 
 probably exist. It is otherwise with the saphenous band, for 
 although I have found it in most foetuses which had reached the 
 fifth or sixth month, yet in those which were older it was 
 unrecognisable, and therefore it may be concluded that it is 
 transitory. The fact that it does exist helps to explain that 
 variety of malposition of the testicle which is called crural in- 
 clusion. Medical literature contains the records of a great many 
 cases of this, and I have to thank Mr Page of Newcastle for 
 having sent me a portrait of a typical example.^ 
 
 In a series of sections of the scrotum and perinseum of a 
 mature foetus, and in which the testes were fully descended 
 (PL III, fig. 54), these perinseal fibres were present, and also 
 others, which united the processus vaginalis to the bottom of the 
 scrotum. There are other circumstances which would render 
 the existence of these perinseal fibres highly probable, even if 
 
 ^ Kocher, Die Krankheiten der Mannliclien GescMecMsorgane, 1887, p. 570 et 
 seq., collates a number of cases of malposition. 
 
104 PROFESSOR C. B. LOCKWOOD. 
 
 the foregoing evidence was wanting. A little while ago it was 
 remarked that the testicle occasionally lay in the perinaBum, 
 and I have before me a sketch, which Mr J. H. Morgan 
 kindly sent me, of a case of a child in which the right half of 
 the scrotum was smaller than the other, and the corresponding 
 testis in the perinseum. But the most significant point in the 
 case was the presence of a band of fibres which held the right 
 testis in the perinseum near the anus. This band, as Mr 
 Morgan's note sajs, was attached near the anus, and caused 
 the skin to pucker when the testicle was pushed. forwards. It 
 seems as though it were a common thing in these cases for the 
 testicle to be held in the perinssum by some sort of a band. 
 Mr Treves has also informed me of a similar case, and in which 
 when the band had been divided with a tenotomy knife, the 
 testicle was replaced in the scrotum. Mr McCarthy ^ mentions 
 a case, and Cloquet, in another, actually had an opportunity of 
 dissecting out the band.^ The perinseal attachments of this 
 band may be either the tuberosity of the ischium, the external 
 sphincter, or the skin. In Cloquet's case it was attached to the 
 tuber ischii. Perhaps it may not be out of place to mention 
 that great caution is requisite in dealing with these cases. 
 There is reason to think that the processus vaginalis may ac- 
 company the testicle in its abnormal excursion, and remain in 
 communication with the general peritoneal sac. The conse- 
 quences which may ensue, if, in the course of operations for the 
 replacement of the testicle, the processus vaginalis was opened 
 wdthout special precautions, are familiar to every surgeon. Mr 
 M'Carthy in his article mentions two deaths from peritonitis 
 after operations upon cases of this kind. 
 
 A last reference to the scrotal fibres of the gubernaculum 
 may be permitted, more especially as doubt has been cast upon 
 their existence.^ Their presence is usually affirmed, because 
 an attempt to draw the newly-descended testis upwards out of 
 the scrotum causes the end of that sac to invert, and, moreover, 
 because they can be seen by dissection.^ Both of these state- 
 
 1 Quain's Lie. of Medicine, 1882, p. 1606. 
 
 ^ Eecherches sur les Causes et I'Anatomie des Hernies Ahdominales, Paris, 1819 
 pp. 24, 25. 3 Bramann, ibid., p. 334. 
 
 * Curling, Diseases of the Testis, 4th ed., 1878, p. 17 et seq. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 105 
 
 merits are, I think, correct ; and, in addition, the presence of 
 scrotal fibres is shown in the series of sections of a fully de- 
 veloped scrotum (PI. III. fig. 54). Nevei^theless, those who 
 have attempted to trace smooth muscle fibres with the scalpel 
 will readily understand why opinions vary. 
 
 It may be advantageous to enumerate the attachments of the 
 gubernaculum in the order in which they seem to develop, 
 viz., (1) abdominal ; (2) pubic and saphenous ; (3) perineeal and 
 scrotal. Placing the saphenous upon one side as being, perhaps, 
 inconstant, the functions attributed to the abdominal, pubic, 
 and scrotal are as follows: — The testicle is brought by the 
 abdominal into the ostium of the processus vaginalis, through 
 th'e^anal by pubic, and deposited in its resting place by the 
 scrotal. With regard to the first of these actions, it may be 
 said that the process is not quite so simple as at first glance it 
 seems to be. If we compare the position of the testicle of a 
 five months' foetus (figs. 50 and 51) with its position in one of the 
 seventh month (fig. 49), it is evident that in the younger embryo 
 the gland lies close to the ostium of the processus vaginalis, 
 whilst in the older embryo it seems to have re-ascended a little 
 way into the abdomen.^ This re-ascent, which seems a constant 
 occurrence, has been permitted by a luxuriant growth of the 
 mesorchium and by an elongation of the intra-abdominal por- 
 tion of the gubernaculum. The occurrence is unexpected, and 
 seems to indicate a peculiarity in the action of the gubernaculum, 
 and, in a sense, to detract from the importance given to its 
 abdominal attachment. By its abdominal attachment the 
 gubernaculum can only for a time hold the vas deferens, and 
 afterwards the epididymis and testicle, near ostium of the pro- 
 cessus vaginalis. The actual passage of the testicle through the 
 inguinal canal begins during the seventh month, and by that 
 time the vaginalis is ready for its reception, and the guber- 
 naculum has acquired other attachments to the pubes, which 
 may be supposed to afford it a fixed point from which to act and 
 draw the gland, first into the ostium, and afterwards into the 
 canal. The scrotal band, however, seems deficient in firm 
 attachments and unfitted for the duty it is supposed to perform. 
 Various circumstances indicate that, in bringing the testicle 
 ^ Bramann, p. 620. 
 
106 PROFESSOR C. B. LOCKWOOD. 
 
 through the abdominal wall, the gubernaculum must exert a 
 certain amount of force. For instance, if a foetus be chosen in 
 which the testicle is about to pass through the abdominal wall, 
 and traction be made upon the gubernaculum, it is clear that as 
 the testicle travels towards the scrotum, not only the mesorchium 
 and its contents and the processus vaginalis, but also the 
 peritonaeum of the back of the abdomen, moves with it. In con- 
 sequence of this locomotion of the serous membrane, the csecum 
 and ilium on the right side, and the sigmoid flexure upon the 
 left, become lower in the abdomen, a circumstance upon which 
 both Scarpa and Wrisberg have commented,^ and as I proceed 
 other reasons for this belief will be forthcoming. Now, it is 
 obvious that the scrotal attachments of the gubernaculum are 
 ill fitted to afford resistance to the action of the muscle, and 
 I conceive that it is by means of its well-attached perinseal 
 fibres that the gubernaculum is enabled to effect its purpose, 
 the scrotal band merely influencing the final position of the 
 gland. 
 
 In attributing the final passage of the testicle through the 
 abdominal wall into the scrotum to the traction of the guber- 
 naculum, I have not thought it necessary to parade the various 
 theories which have been offered as an explanation of the phe- 
 nomenon. The weight of the organ has been invoked, also 
 certain suppositious respiratory efforts, and, finally, a sort of 
 hernial protrusion.^ The first of these theories has been de- 
 molished by Sappey, who remarks that during the period of 
 transition the foetus usually lies in the uterus with its head 
 downwards. The second theory calls for no comment, for there 
 is nothing to show that the foetus breathes before birth ; rather 
 the contrary. The last theory is more plausible, and has 
 recently been revived,^ but seems to rest upon an obvious 
 ambiguity. The term hernia is used in two different senses. 
 Sometimes it implies merely an anatomical condition, namely, 
 the escape of organs from their containing cavities ; at other 
 times the word hernia is used to connote a pathological change ; 
 but, used in its pathological and not in its anatomical sense, it 
 
 ^ See paper by author, Roy. Med. Chir. Trans., vol. Ixix. p. 505. 
 
 ^ Sappey, TraiM d'Anatomie Descriptive, vol. iv. p. 606. 
 
 2 J. Bland Sutton, An Introduction to General Pathology, 1886. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 107 
 
 is clear that the word hernia ought not to be used in explaining 
 the transition of the testicle, for the simple reason that the 
 pathology of hernia is quite undecided. The question still 
 remains to be settled whether inguinal hernia is due to (a) a 
 defect in the abdominal walls ; (6) an elongation of the 
 mesentery ; or (c) a general defect of the peritoneum. However 
 this may be, I hope presently to adduce evidence to show that 
 the gubernaculum testis may have something to do with the 
 pathology of congenital csecocele and of infantile hernia. 
 
 The Cremaster. 
 
 The anatomy of the cremaster is well known, and does not 
 call for lengthy notice. Where its fibres are attached to 
 Poupart's ligament, they are also continuous with the internal 
 oblique muscle. Its inner tendinous attachment is into the 
 pubes, close to the insertion of the internal oblique muscle.^ Its 
 loops descend in front of the spermatic cord, and become larger 
 and longer as they descend, and some of them may invest the 
 testicle. Upon these points there is perhaps no dispute, but a 
 variety of opinions prevail as to the parentage of the muscle. 
 It would not be inaccurate to say that there are two main views 
 upon this question. Some think that the cremaster is created 
 out of those striped muscular fibres which ascend the guber- 
 naculum from the abdominal wall, and which I have called the 
 ascending cremaster. Others believe that it is derived from the 
 lower fibres of the internal oblique, and which have accompanied 
 the testis in its transition. The first of these opinions origi- 
 nated with Hunter, who saw that the fibres of the ascending 
 cremaster of the ram became inverted when the gubernaculum 
 was pulled downwards beyond the abdominal wall.^ Judging 
 from its characters in the human embryos which have been 
 described above, it is probable that this same thing would happen 
 to them. I have assumed in the foregoing that the chief labour 
 of transition falls upon the smooth muscular elements of the 
 
 1 Quain, 9tli ed., 1882, vol. i. p. 327. 
 
 2 A very clear and correct account of the cremaster is given by Debierre and 
 Pravaz {Lyon Mklicalc, 1886), so far as tbe muscle can be studied by dissection. 
 They also give an excellent epitome of the views of the various authors. 
 
108 PROFESSOR C. B. LOCKWOOD. 
 
 cremaster. It cannot be denied, however, that the striped fibres 
 may also assist and help to draw the testicle as far as their own 
 lower attachments, but obviously not beyond, as some have 
 supposed. The ascending cremaster of the human embryo is so 
 trivial, that perhaps it ought to be looked upon as a mere 
 survival of a muscle which, in some of the lower animals, is more 
 active and better developed. 
 
 We now come to the second theory, that the cremaster is an 
 appendage of the internal oblique muscle, displaced towards the 
 scrotum by the testicle in its transition. From what has gone 
 before it will be seen that this proposition is only true in a 
 very limited sense, namely, so far as it may be taken to imply 
 that the descending cremaster is developed in connection with 
 the oblique muscle. The histological specimens which have 
 been described in the earlier part of this lecture seemed to 
 show that the muscular fibres, which were called the ascend- 
 ing cremaster, developed in close connection with the internal 
 oblique ; perhaps it would not be incorrect to say that they 
 developed as an outgrowth of that muscle. But it must not be 
 ignored that, at first, no distinction can be drawn between the 
 internal oblique and transversalis muscles, so that the latter 
 might claim a share in the process. However, the part of the 
 proposition which attributes the origin of the cremaster to the 
 transition of the testicle is not borne out by the specimens. 
 They show that the external cremaster develops long before 
 that event, and indeed before the processus vaginalis has ap- 
 peared. Towards the end of the seventh month of intrauterine 
 life the processus vaginalis is so far ahead of the testicle that it 
 must have anticipated the testicle in any action that organ 
 might have had in carrying down the cremaster. It would be 
 more rational to attribute the formation of the muscle to the 
 gradual advance of the peritoneal pouch, rather than to that of 
 the sexual gland. In the later stages, towards the eighth month 
 of intrauterine life, the processus vaginalis is so voluminous that 
 it would be rash to deny it a part in at least modifying the 
 cremaster ; but it is so difficult, perhaps impossible, to dissect 
 the muscle in the foetus, that I have been unable to obtain 
 definite information upon this point. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 109 
 
 The Superior Attachments of the Guhernaculum, the 
 Mesorchium, and Plica Vascularis. 
 
 The superior attachments of the gubernaculum have already 
 been described, with the exception of the peritoneal prolonga- 
 tion. It may be remembered that they varied according to the 
 stage of development, the gubernaculum being attached first to 
 the genital cord, then to the cord and epididymis, and finally 
 to both of those structures, and also to the body of the testicle. 
 The prolongation which the gubernaculum sends upwards be- 
 hind the testicle to the peritoneum is chiefly confined to the 
 plica vascularis, but it has sometimes a wider distribution. It 
 was well marked in a foetus 8| inches long (legs extended), and 
 presumably of about the sixth month ; and in others, 12 inches 
 long, and presumably towards the end of the seventh month, 
 the plica vascularis contained its fibres in great abundance, and 
 they probably reached the organs with which the fold is at 
 various times conuected, namely, on the right side with the 
 caecum, vermiform appendix, or the ilium and mesentery, and 
 on the left side with the sigmoid flexure. Without doubt, the 
 main portion passes to the mesentery, which, at the eighth 
 month, is common to the ceecum and ilium, or to the mesentery 
 of the sigmoid flexure. Both the plica vascularis and its con- 
 tents, especially the muscular fibres, are of physiological and 
 pathological importance. When the lower end of the right 
 gubernaculum of the foetus of the seventh or eighth month, 
 whose mesorchium has been figured in an earlier part of this 
 lecture (fig. 49), was pulled downwards, the processus vaginalis, 
 vas deferens, epididymis, testicle, mesorchium, with its plica 
 gubernatrix and plica vascularis, the caecum and vermiform 
 appendix, the ilium and mesentery, and peritoneum of the back 
 of the abdomen, all glided downwards towards the inguinal 
 canal and scrotum, and traction on the left gubernaculum had 
 the same effect upon the sigmoid flexure. The attachment of 
 the gubernaculum to the various parts of the sexual apparatus 
 is sufficient to account for their displacement, and the other 
 viscera follow, because they are connected with the epididymis 
 by the plica vascularis. Doubtless, the serous naembrane of 
 
110 PROFESSOR C. B. LOCKWOOD. 
 
 that fold may be sufficiently inelastic to bear whatever strain 
 there may be, but presently it will be seen that due regard 
 must be paid to the upward prolongation of the gubernaculum. 
 These muscular fibres have an extensive connection with the 
 peritoneum, which lines the back of the abdomen, and doubt- 
 less bring about the locomotion of that membrane, which is 
 seen in the transition of the testicle, and in many cases of 
 hernia. That the serous membrane of the back wall of the 
 abdomen is much looser than the rest has been repeatedly 
 pointed out in the earlier part of this lecture ; it is underlaid by 
 abundant loose areolar tissue and fat, and is easily displaced 
 and thrown in folds. The peritoneum, which lines the front 
 wall of the abdomen, is, except near the epigastric and hypo- 
 gastric arteries, intimately bound to the abdominal wall. In 
 adult subjects the union of transversalis muscle, transversalis 
 fascia, and peritoneum is so close, that sometimes it would 
 hardly be incorrect to say that the muscular fibres of the trans- 
 versalis were inserted into the peritoneum. For these reasons 
 the peritoneum of the front wall of the abdomen is incapable of 
 much displacement, and probably takes but a small share in the 
 formation of large hernial sacs. 
 
 Before discussing the other attributes of the muscular fibres, 
 the history of the plica vascularis, considered as a serous fold, 
 may be mentioned. When the testicle glides down the pro- 
 cessus vaginalis — which has preceded it — into the scrotum, it 
 retains in a greater or less degree its peritoneal folds. For 
 instance, at its lower end may still be seen in most foetuses the 
 plica gubernatrix, and from the head of the epididymis another 
 fold, the plica vascularis, runs upwards upon the back of the 
 processus vaginalis towards the abdomen. Owing to its connec- 
 tion with the globus major the plica vascularis is easy to 
 recognise, and it not uncommonly persists throughout life. For 
 instance, Camper,^ in his Icones Herniarumn, gives excellent 
 representations of it ; Sir Astley Cooper also depicts it ; ^ and 
 Sappey ^ says that the visceral layer of the tunica vaginalis 
 
 1 Camper, Icones Herniarum, ed. by S. J. Scemmerring, 1801, Tab. III. figs. 
 3 and 4. 
 
 ^ Cooper, Anatomy and Surgical Treatment of Abdominal Hernia, pi. v. 
 fig. 6, and elsewhere. 
 
 3 Trait6 d' Anatomic Descriptive, vol. iv. p. 602. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. Ill 
 
 forms a sort of small mesentery, which contains the testicular 
 vessels ; but none of these authors seem to have recognised the 
 developmental significance of this fold. The plica vascularis is 
 usually distinct in a foetus in which the testicles have just 
 reached the scrotum, and it extends upwards along the back of 
 the processus vaginalis into the abdomen (fig. 45) ; or, if that 
 passage has been obliterated, a fold, which occupies its position, 
 extends from the internal abdominal ring towards the mesentery 
 either of the caecum and ilium, or of the sigmoid flexure. The 
 main interest of the plica vascularis depends upon its relation to 
 undescended testis and various forms of congenital hernia. 
 
 That the transition of the testis may have an influence upon 
 the last stages of the migration of the caecum I have elsewhere 
 endeavoured to show,^ and have published cases in which, when 
 the testicle was undescended and lay within the abdomen, the 
 csecum remained at or near the liver. On the other hand, I 
 have met with a case in which the right testicle was fully 
 descended, although the caecum was firmly adherent to the 
 liver.2 This abnormality occurred in an anencephalic monster, 
 and I am accustomed always to examine these creatures with 
 care, because they seem particularly liable to intrauterine peri- 
 tonitis and other complaints, and therefore afford most interesting- 
 material. The foregoing case has been mentioned, because it 
 tends to place the matter in a light not very favourable to my 
 hypothesis, but not, however, in an absolutely unfavourable 
 light. In the first place, it has merely been claimed that the 
 testicle in its transition influenced the last stages of the 
 migration of the csecum, and in the case w^hich has been men- 
 tioned the caecum must have become adherent to the liver at 
 such an early age, that it could neither have been infiuenced 
 by the movements of the testicle, nor by its own adherence have 
 impeded that organ. Continuing the pathological bearings of 
 the plica vascularis, there is reason to believe that that fold may 
 in another way be a factor in the pathology of undescended 
 testicle. In reading of cases of abdominal inclusion of the 
 testicle, it is impossible not to be struck by the repeated 
 
 ^ "Abnormalities of the Ctecuin and Colon, with Reference to Development," 
 British Medical Journal, September 1882, p. 575. 
 
 2 The specimen is described in Path. Soc. Trans., vol. xxxvii. p. 250, and is 
 in the museum of St Bartholomew's Hospital. 
 
112 PKOFESSOR C. B. LOCKWOOD. 
 
 references to the presence of adhesions. Without doubt some 
 of these are simply inflammatory,^ due to intrauterine peri- 
 tonitis ; 2 but in others it seems safe to infer that the so-called 
 adhesion was in reality the plica vascularis which had persisted 
 in an unusual degree. Such a case as the following is not 
 without significance : — Cloquet found in an aged man the left 
 testicle an inch inside the ring, and fastened to the sigmoid 
 flexure by a band — fibrous, white, round, and very strong.^ 
 Curling mentions another case of imperfect transition, in which 
 the testicle was adherent to the gut, but his observation is based 
 upon clinical evidence,* and I am unable to ascertain that he 
 clearly appreciated that the so-called adhesion was of the nature 
 of the plica vascularis. However, he agrees with Cloquet in 
 believing that congenital bands, which seem to possess the 
 characters of the plica vascularis, may impede the transition of 
 the testicle. 
 
 The plica vascularis seems at times to play a different part. 
 It occasionally happens that the csecum, vermiform appendix, 
 ilium, or sigmoid flexure may accompany the testicle into the 
 scrotum, and give rise to various forms of congenital hernia. 
 In cases of this sort a peritoneal band is very often found 
 passing upward from the head of the epididymis to the herniated 
 gut. The spermatic vessels usually lie in this fold, and it has 
 the characters of the plica vascularis. Wrisberg,^ Lobstein,^ 
 Sandifort,'' and others ^ have mentioned this circumstance, and 
 the first and last named authors seemed to appreciate clearly 
 
 ^ Testicle retained in the abdomen by adhesion to the sigmoid flexure of the 
 colon. John Wood, "Adhesions due to Inflammation from Mesenteric Disease 
 in Foetal Life," Path. Trans., vol. viii., 1856, p. 265. 
 
 2 Simpson, Ed. Med. Jour., vol. lii. ]). 17 et seq. We have also to note the 
 possibilitj'' that the retained testicle may in some rare cases set up inflammation 
 in its vicinity. 
 
 ^ Recherches sur les Causes et TAnatomie des Hernies Ahdominales, Paris, 1819, 
 p. 23. 
 
 4 Ihid., p. 24. 
 
 s Wrisberg, " Observationes Anatomicse de Testiculorum ex Abdominse in 
 Scrotum descensu," &c., Comment. Sac. Beg. Scient., Getting., 1800, p. 173 et 
 seq. 
 
 ^ Quoted by Wrisberg. 
 
 '' Sandifort, Icones Hernice Ingidnales Congenitce, 1781, p. 12 et seq. 
 
 8 Scarpa, On Hernia, Wishart, Edinburgh, 1814, p. 194, art. on the "Natural 
 Fleshy Adhesion"; also F. Treves, "Hernia of the Caecum," Brit. Med. 
 Jour., Feb. 19, 1887, p. 385. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 113 
 
 the meaning of the connection between the gut and the testicle. 
 They assumed that, owing to persistence of the plica, the gut 
 had been dragged down by the testicle in its transition. How- 
 ever, although there is an element of truth in this assumption, 
 there is reason to doubt whether it is the whole truth. I have 
 mentioned elsewhere ^ a congenital csecocele, which I was so 
 fortunate as to find in an infant, and in which there was no fold 
 extending from the testicle to the gut, but in its place a 
 quantity of unstriped muscular fibres, which turned upwards 
 from the perinasum and back of the testicle towards the csecum 
 and peritoneum of the back of the abdomen. These muscular 
 fibres are clearly the upward prolongation of the gubernaculum, 
 which has already been mentioned, and which has been claimed 
 to aid in the locomotion of the peritoneum of the back of the 
 abdomen which accompanies the transition of the testicle. In 
 this respect they seem to have had a share in causing the 
 cgecocele. In another csecocele sent to me by my friend, Mr 
 Maud, the muscular band was also present ; and Professor 
 Cunningham has very kindly written to inform me of a case in 
 which there was a band of fibres so strong "that it does not 
 fall far short of the platysma," and which he considers "as 
 having been the active agent in producing the hernia (of the 
 caecum), and as having become hypertrophied in the process." 
 In this case there was also a second isolated peritoneal pouch, 
 which I will mention again in speaking of infantile hernia. 
 
 The upward prolongation of the gubernaculum is also met 
 with under other circumstances. Normally it persists as the 
 muscular fibres which Henle and Cruveilhier call the internal 
 cremaster ; ^ and presently it will be seen to have an important 
 bearing upon the pathology of infantile hernia. But before men- 
 tioning this, perhaps I may point out that the plica vascularis 
 is found very commonly in congenital and funicular hernia, and 
 is an important guide to the position of the spermatic vessels. 
 It is unnecessary to point out M^hat serious results ensue when 
 these vessels are injured in the performance of operations. 
 
 1 Med. Cliir. Trans., vol. Ixix. p. 505. 
 
 2 Since my paper upon Encysted and Infantile Hernia, and in which this view 
 was put forth, a similar observation has been made quite independently by 
 Debierre and Pravaz {ibid., p. 143), but without reference to hernia. 
 
 H 
 
114 PROFESSOR C. B. LOCKWOOD. 
 
 The peritoneal prolongation of the gubemaculum is, I think, 
 an important factor in producing certain sorts of hernial sacs, 
 especially the sacs of infantile hernia. This opinion is based 
 upon evidence derived from such specimens as the following : — 
 There is a specimen in the museum of St Bartholomew's 
 Hospital,! which I have had the opportunity of dissecting, in 
 which the processus vaginalis is represented by a long tube, 
 which extends from the internal abdominal ring to just above 
 the epididymis. This tube communicates with the general 
 cavity of the peritoneum by a small aperture, a quarter of an 
 inch in diameter, which occupies the usual position of the 
 internal abdominal ring external to the epigastric artery. A 
 probe introduced into this opening showed that the processus 
 vaginalis was occluded an inch from the upper end, but in the 
 remainder of its extent its cavity was almost half an inch in 
 diameter above and one and a half below. Behind the superior 
 part of this serous tube a hernial sac protruded from the peri- 
 toneum in such a way that the anterior wall bulged slightly 
 into the cavity of the processus vaginalis. Attached to the 
 lower extremity of this protrusion and to its posterior wall were 
 strong bands of unstriped muscle fibre intimately related to the 
 spermatic vessels. The end of the sac to which these were 
 attached was conical and sharply-pointed. This specimen I 
 have described elsewhere, and considered it to have been a 
 variety of infantile hernia.^ It is perhaps unnecessary to argtie 
 that the origin of the pointed hernial sac was due to the 
 action of the muscular fibres, and, further, that these fibres 
 were a part of the peritoneal prolongation of the gubernaculum. 
 The isolated peritoneal pouch seen in Professor Cunningham's 
 specimen lay towards the outer side of the true sac of the con- 
 genital csecocele ; and although it had no connection with the 
 abdominal peritoneum, " was drawn out above into a fine point 
 
 and has doubtless been dragged down by some stray 
 
 fibres" (of the gubernaculum). In other cases of infantile 
 hernia the band is also clearly marked, and it may perhaps 
 suffice to mention a single well-marked instance. By an 
 infantile hernia is meant a variety of congenital hernia, in which 
 the processus vaginalis is not obliterated, but remains in the 
 1 Sp. 2140b. 2 jifg^_ c%j,y_ Trans., vol. Ixix. p, 513. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 115 
 
 condition in which it is found in congenital hernia, except that 
 it may be occluded to a greater or less degree near the internal 
 abdominal ring. However, occlusion is probably the exception, 
 and when it does take place the manner of its occurrence can 
 be traced. In addition to this non- obliteration of the processus 
 vaginalis there is, in infantile hernia, a second pouch of peri- 
 toneum, which descends behind the other and bulges into it. 
 Sometimes the projection is slight, but at others is so great 
 
 Fig. 55. — Infantile Hernia. A, upward prolongation of gubernaculum with 
 spermatic artery in its midst ; B, true spinal sac with double walls ; C, body 
 of testicle. 
 
 that the true hernial sac — i.e., that which contains the herniated 
 viscus — almost seems to hang from near the ostium of the pro- 
 cessus vaginalis, like a sac pendent from the ring. It may 
 render this brief description clearer if I add that, to gain an 
 entrance into the true hernial sac from in front, it would be 
 necessary, first of all, to cut the front and back walls of the non- 
 obliterated processus vaginalis, and then the wall of the true 
 
116 PEOFESSOE, C. B. LOCKWOOD. 
 
 hernial sac, as Hey^ calls it. There is reason, however, to 
 believe that the pathology of infantile hernia is in some way 
 connected with the plica vascularis, because in some specimens 
 the remains of that fold can be seen extending from the 
 epididymis to the lower end of the true hernial sac.^ In other 
 cases, in which the serous membrane has probably been dis- 
 sected away, instead of the plica a strong band of smooth 
 muscle fibres unites the back of the epididymis to the ex- 
 tremity of the true hernial sac (see fig. 55). This band 
 represents the peritoneal prolongation of the gubernaculum, 
 and, besides being intimately related to the spermatic vessels, 
 runs upwards along the back of the true hernial sac tow^ards 
 the abdomen. When we recall the influence which the guber- 
 naculum has in forming the processus vaginalis itself, or, as 
 Cloquet has maintained, hernial sacs of various sorts, it seems 
 reasonable to argue that it is an important factor in the patho- 
 logy of infantile hernia. 
 
 Relation of the Vas Deferens and SperTnatic Vessels to Pro- 
 cessus Vaginalis. The Recurrent Branches of the Sper- 
 matic Artery. 
 
 It is unnecessary to premise, that as the testicles migrate 
 down the processus vaginalis, the spermatic vessels and vas 
 deferens accompany them, and acquire certain definite 
 relations which it is important to recognise. If a foetus be 
 chosen in which the testicles have completed their migration, 
 but in which the processus vaginalis is capacious and still in 
 communication with the peritoneum, the relations of the vas 
 deferens and spermatic vessels are usually as follows: — The 
 artery and vein run from the upper part of the abdomen to the 
 outer side of the ostium of the processus vaginalis, and then along 
 the back of that sac, lying in the plica vascularis, as far as the 
 epididymis, where they divide into their two main divisions, one 
 going to the bod};' of the testicle and the other to epididjanis ; 
 the vein usually lies to the inner side of the artery. The vas 
 
 1 It is interesting to note that in Hey's case of infantile hernia the sac con- 
 tained the csecuni. 
 
 ^ E.g., Sp. R. 24, St Thomas's Hos. Museum, Med. Chir. Trans., fig. 4, p. 
 493. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 117 
 
 deferens, on the other hand, runs upwards from the neck of the 
 bladder round the hjrpogastric arteries towards the inner and 
 lower part of the ostium of the processus vaginalis, and thence 
 along the posterior wall of that sac, to reach the globus minor. 
 In the last part of its course the vas deferens lies internal to 
 the vessels, and sometimes quite apart from them (fig. 56). 
 These relations are interesting, because they help to explain 
 the separation of the vas deferens from spermatic vessels seen 
 in many cases of hernia. The London museums contain so 
 many examples of this condition, and it seems such a common 
 and well-known occurrence, that it is perhaps unnecessary to 
 adduce instances ; but in nearly all of them the vas deferens 
 lies well to the inner side of the vein and artery. Lawrence ^ 
 mentions numerous instances of this occurrence, and attributes 
 the separation to the distensile force of the hernia. Later, he 
 says the same condition may be found in a small hernial 
 tumour,2 and the specimens in museums fully bear out this 
 statement ; and they further suggest that mere distension could 
 not have been the sole cause of the separation of the vas from 
 the vessels, but that the predisposing developmental factor 
 which has just been mentioned must also be taken into con- 
 sideration; indeed, in some instances of congenital hernia, it 
 seems as if the structures in question can never have been 
 together. I hope to deal with this question more fully at 
 another time, and will therefore not endeavour at present to 
 discuss other varieties of the condition. 
 
 In endeavouring to ascertain whether the spermatic artery 
 accompanies the transition of the testicle pari 'passu with the 
 peritoneum and processus vaginalis, or whether it was drawn in 
 a greater degree towards the scrotum, several interesting cir- 
 cumstances came to light. Text-books on anatomy usually 
 state that the spermatic artery gives branches to the peritoneum, 
 and on the left side others are frequently supplied to the sigmoid 
 flexure.^ It suggests itself that these branches may afford 
 information bearing upon the question of the relative move- 
 
 ^ Lawrence, On Hernia, p. 212. 
 
 2 Ibid., p. 213. 
 
 ^ See more particularly Turner on the existence of an anastomosing sj^stem of 
 arteries between the visceral and parietal branches of the abdominal aorta, Brit, 
 and For. Med. Chir. Review, July 1863. 
 
118 PROFESSOR C. B. LOCKWOOD. 
 
 ments of the artery and of the peritoneum ; and in numerous 
 dissections I have found the spermatic arteries give off 
 recurrent branches to the peritoneum. The largest of these 
 begin near the internal abdominal ring, and run 4 or 5 
 inches upwards, giving off branches and gradually dwindling 
 (PL III. fig. 56). The inference to be drawn from their presence 
 seems obvious, namely, that the spermatic artery is displaced 
 more than the peritoneum. But, in addition, the recurrent 
 branches of the spermatic artery seem to have a pathological 
 bearing, and it is not improbable that they have something to 
 do with the formation of these secondary pouches, which are 
 found upon the hinder wall of the sacs of some congenital 
 hernia. That these recurrent branches may be also found at 
 the back of the processus vaginalis is shown by various speci- 
 mens. For instance, there is a dried hydrocele in St Bartholo- 
 mew's Hospital Museum whose vessels have been injected, and 
 in which the recurrent branches are quite clear ;i also, there 
 is in the Dupuytren Museum a hernial sac, which has been 
 treated in the same way, and which has the same recurrent 
 arteries upon its hinder wall.^ Now, the principle seems 
 established that vessels which are related as these recurrent 
 branches are to the peritoneum may throw that membrane into 
 folds,^ and it is not without significance to note that I have 
 found a large obliterated vessel running in the fold of serous 
 membrane, which formed a supplementary sac upon the back 
 wall of a funicular hernia.^ 
 
 The Closure of the Processus Vaginalis. 
 
 A number of foetuses have been examined to see how the pro- 
 cessus vaginalis becomes occluded after it has transmitted the 
 testicle. There seems to be, as others have remarked, a strong 
 tendency for it to close in two places, which are some distance 
 apart, namely, just above the testicle and near the internal 
 
 1 2753. 2 Sp. 295. 
 
 ^ Treves, The Anatomy of the Intestinal Canal and Peritoneum in Man, 
 London, 1885. 
 
 * This specimen, and another which is of exactly the same nature, are in the 
 museum of St Bartholomew's Hospital, Nos. 2090 and 2140e. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS, 119 
 
 abdominal ring. This statement is founded upon ordinary ana- 
 tomical evidence, the processus having been merely slit open with 
 scissors. In some foetuses the serous canal was so attenuated 
 that it was hard to discern, and it would have been rash to make 
 any positive statement as to its patency or occlusion. But there 
 was no evidence in any case to show that the processus vaginalis 
 closed by adhesion. Its interior was always smooth and shining, 
 like the rest of the peritoneum. Importance attaches to this 
 point, because it has been thought that the processus vaginalis 
 sometimes became closed by adhesions which afterwards became 
 stretched into the sac of an encysted hernia. I have elsewhere 
 endeavoured to combat this view upon various grounds, amongst 
 which, perhaps, the most cogent are, first, that such adhesions 
 have never been seen ; and second, that the specimens which 
 have been called encysted hernise belong to the infantile variety. 
 In bringing these lectures to a close, I wish to thank Mr 
 D'Arcy Power and numerous other friends for the valuable 
 material they have placed at my disposal. And I am especially 
 indebted to Dr Vincent D. Harris for many acts of kindness, 
 and for his assistance and advice. 
 
 EXPLANATION OF PLATES AND OF WOODCUTS. 
 Explanation of Plate I. 
 
 Ao. Aorta. 
 
 Co. Cardinal vein. 
 
 So. Somatopleure. 
 
 Sp. Splanchnopleure. 
 
 JSp. Epiblast. 
 
 lit/. Hypoblast. 
 
 £.w. Body wall. 
 
 M.S. Medulla spinalis. 
 
 M. Mesentery. 
 
 I.m. Intermediate cell mass. 
 
 T. Epiblastic thickenings. 
 
 Figs, 1 to 4. Embryo chick, 48 hours. — Fig. 1. Connection of 
 
 "Wolffian duct with somite. Fig. 2. Connection of Wolffian duct with 
 
 intermediate cell mass. Figs. 3 and 4. Epiblastic thickenings. 
 X about 120. 
 
 s. 
 
 Somite. 
 
 I. cm. 
 
 Intermediate cell mass 
 
 W.d. 
 
 Wolffian duct. 
 
 W.t. 
 
 Wolffian tubule. 
 
 N.s. 
 
 Nephrostomata. 
 
 GL 
 
 Glomerulus. 
 
 Nc. 
 
 Notochord. 
 
 L. 
 
 Liver. 
 
 P. 
 
 Projection. 
 
 R. 
 
 Recess. 
 
 Sp.c. 
 
 Spinal canal. 
 
120 PEOFESSOE C. B. LOCKWOOD. 
 
 Fig. 5. Nine days' rabbit's embryo. Epiblastic thickenings and 
 Wolffian duct and tubules coexist. x 80. 
 
 Fig. 6. Rabbit's embryo, 8th. day. Intermediate cell mass. x 
 about 50. 
 
 Fig. 7. Rabbit's embryo, 8th day. Communication between body 
 cavity and interior of somite. 
 
 Figs. 8, 9, and 10. Rabbit's embryo, 9th day. x 180.— Fig. 8. 
 Intermediate cell mass and its connection with lining of the body 
 cavity. Fig. 9. Origin of Wolffian duct and tubule. Connection 
 of tubule with the peritoneum. Epiblastic thickening over somite. 
 Fig. 10. Hinder tubule imunited to peritoneum. 
 
 Figs. 11 and 12. Urogenital ridge of a rabbit's embryo of 10th day. 
 X 250. — Fig. 11. Longitudinal section of Wolffian duct and tubules. 
 Fig. 12. Transverse sections. To show the formation of lumen in 
 tubules. 
 
 Figs. 13, 14, 15, and 16. x 120. Urogenital ridge of rabbit's 
 embryo at commencement of 13th day. Termination of Wolffian 
 duct and structures supposed to represent a pronephros. 
 
 Figs. 17, 18, and 19. Urogenital ridge of human embryos. 
 X about 100. — Fig. 17. Germinal epithelium. Fig. 18. End of 
 Wolffian duct — Solid column of cells. Fig. 19. Wolffian tubule 
 united to peritoneal epithelium. 
 
 Fig. 20. Urogenital ridge of human embryo about 30th day. Con- 
 nection of epithelium of the body cavity and that of the Wolffian duct. 
 
 Figs. 21 and 22. Human embryo of about 30 days. Fore-part of 
 Wolffian body. Projections into body cavity, and joining of peri- 
 toneal epithelium with those of the Wolffian tubules. 
 
 Explanation op Plate II. 
 
 Fig. 23. Glomerulus of human Wolffian body. Gl, glomerulus ; T, 
 Wolffian tubule ; V, afferent and efferent vessels. 7 Hartnack. 4 Eye p. 
 
 Fig. 24. Glomerulus of human Wolffian body, seventh week, 
 showing the commencement of the development of capillaries in the 
 glomerulus, the formation of the parenchyma and the tubules. P, 
 parenchyma; T, tubule; Gl, glomerulus; C, capillaries ; E, epithelium 
 of a commencing tubule. 7 Hartnack. 4 Eye p. 
 
 Fig. 25. Glomerulus of human Wolffian body at tenth week, showing 
 vascularity of glomerulus and stroma of Wolffian body. Pr, paren- 
 chyma; 6r^, glomerulus; l^T, Wolffian tubule. 7 Hartuack. 4 Eye p. 
 
 Fig. 26. Sexual eminence of rabbit, ~ in oil immersion, to show 
 relation of surface epithelium to meshes of stroma. This drawing 
 was from a section close to that shown in fig. 37, p. 39. 
 
 Fig. 27. Urogenital ridge of rabbit, beginning of thirteenth day. 
 M, mesentery ; GU, germinal epithelium ; WT, Wolffian tubule ; 
 WI>, Wolffian duct; AO, aorta. 7 Hartnack. 4 Eye p. 
 
THE DEVELOPMENT AND TRANSITION OF THE TESTIS. 121 
 
 Fig. 28. Human embryo, sexual eminence. GE, gei-minal epi- 
 thelium ; CF, cardinal vein; WD, Wolffian duct; Gl, glomerulus. 
 The bulk of the lu-ogenital ridge and its genital eminence consists 
 of mesoblastic cells of various shapes — round, branched, and elongated ; 
 these have not been delineated. 7 Hartnack. 4 Eye p. 
 
 Fig. 29. Kidney and hinder part of the Wolffian body of a rabbit 
 of thirteenth day. KB, kidney blastema; TJ, ureter; LCT, loose 
 tissue, which surrounds kidney blastema ; WD, Wolffian duct ; WT, 
 Wolffian tubules ; PC, peritoneal cavity. x 70. 
 
 Fig. 30. Rabbit, fourteenth day, to show relation of hinder part 
 of the Wolffian body and genital mass to one another, and to the 
 kidney which has just appeared. GM, genital mass ; AO, aorta ; K, 
 kidney ; HL, hind limb ; M, mesentery. x 25. 
 
 Fig. 31. Human embryo, thirty-five days. GM, genital mass; 
 K, kidney, lower end ; A 0, aorta ; C F, cardinal vein ; WT, Wolffian 
 tubules ; Gl, glomerulus. x 45. 
 
 Fig. 32. Genital mass of rabbit, commencement of fourteenth day, 
 to show stroma of branched anastomosing cells, and large, pale, 
 granular cells in its meshes. 7 Hartnack. 4 Eye p. 
 
 Fig. 33. Testicle and epididymis of human embryo, at about the 
 twelfth week of intraiiterine life. The section is not quite longi- 
 tudinal. X 25. tST, seminal tubules ; RT, rete testes ; Mesor., 
 mesorchium ; Vas. Def., vasa deferens ; VE, vasa efFerentia ; IT^ 
 indifferent tissue ; TA, tunica albuginea. 
 
 Fig. 34. Outermost and front part of the same human Wolffian 
 body as that which has been drawn in fig. 39, p. 52. WD, Wolffian 
 duct ; CT, collecting tube ; TE, tubuli efferentia ; GM, genital 
 mass. X 45. 
 
 Fig. 35. Human foetus, eight months, to show the cell strings of 
 the mediastinum testes which unite tubules of epididymis to semini- 
 ferous tubules. TE, tubules of epididymis; MT, mediastinum testes; 
 ST, seminal tubules ; V, blood-vessels. x 45. 
 
 Fig. 36. Human testicle showing four vasa aberrantia. T, 
 testicle ; Hy, hydatid of Morgagni ; VD, vas deferens ; Ep, epi- 
 didymis ; 1, 2, 3, and 4, vasa aberrantia. 
 
 Explanation of Plate III. 
 
 Fig. 42. Opening of oviduct of embryo pig into peritoneal cavity. 
 Ov., oviduct ; W.B., Wolffian body ; Lng., lung ; M., mesentery. 
 
 Fig. 43. Oviduct, where its lumen begins. Letters the same as 
 fig. 42. I. P., inner process; W.G., Wolffian glomeruli. 
 
 Fig. 44. Oviduct near it hinder end. Letters the same as figs. 42 
 and 43. O.D., oviduct ; G.M., genital mass. 
 
 Fig. 45. A, B, and C, testicles of human foetuses ; P. V., plica vas- 
 cularis; O.Z)., remains of oviduct; S.Hy., spatulate hydatid. Hy., 
 hydatid of oviduct. 
 
 I 
 
122 PROFESSOR C. B. LOGKWOOD ON THE TESTIS. 
 
 Fig. 46. Pelvic and lumbar regions of a human embryo of seventh 
 week; R., ribs 11th and 12th; Sup. E., suprarenal body; K., 
 kidney ; G.M., genital mass ; W.B., Wolffian body ; II. , ilium ; Isch., 
 ischium ; Fem., femur ; Glut., gluteus maximus ; ^S*^., stomach. 
 
 Fig. 48. Human embrj'o of three months to show plica gubernatrix 
 and position of testis ; x 3. I'., testicles; ^., kidney; /., intestine; 
 P. v., plica vascularis; G.O., right and left genital cords; G.G.C., 
 common genital cords; B., bladder; Guh., plica gubernatrix and 
 gubemaculum. 
 
 Fig. 50. Ostium of processus vaginalis at fifth month. Tes.y 
 testicle; V.D., vas deferens; Guh., gubernaculum ; P.G., plica 
 gubernatrix ; P.V., processus vaginalis ; C, loose cellular tissue ; II. 
 Ves., iliac vessel ; Int. Ob. and Trans., internal oblique and transver- 
 salis muscles ; Fx. Ob., external oblique. 
 
 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.I., anterior superior spine of ilium; B. bladder; 
 Ry. A., hypogastric arteries ; T., testicle ; G., gubernaculum ; Ps., 
 psoas ; II., iliacus ; Int. 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 ; Cce., csecum ; P. 
 Vag., processus vaginalis; P., pubic bone ; PI. Vas., plica vascularis ; 
 Ep., epididymis; Tes., testicle; PI. Gub., plica gubernatrix; Gub., 
 gubernaculum ; Per., perineal fibres of the gubernaculum testis. 
 
 Fig. 56. Processus vaginalis at eighth month of intrauterine life 
 to show the relations of the vas deferens and spermatic vessels to 
 its posterior wall ; aS'. V., spermatic vessels ; V.D., vas deferens ; 
 Ep., epididymis ; Tes., testicle ; Gh., gubernaculum. 
 
 Fig. 57. Eecurring branches of spermatic artery; 8. A. and V., 
 spermatic artery and vein ; S., sigmoid flexure. 
 
 ERRATA. 
 
 Page 48, line 23, /or 32 read 31. 
 „ 65, „ 10, for 23 read 33. 
 „ 65, „ 15, /or 23 rmc? 33. 
 
 PRnfTED BY NEILL AND COMPANY, EDINBURGH. 
 
WD. 
 
 
 ■s? ss 
 
 DEVELOP M 
 
PL I. 
 
 FHul>i,Lith'Ediii' 
 
 T OF TESTIS. 
 
PL.!/. 
 
 F.Huth.Litn'Edin'^ 
 
M ,1 
 
PL HI. 
 
 y.Huth.Lift'Edin' 
 
COLUMBIA UNIVERSITY LIBRARIES 
 
 This book is due on the date indicated below, or at the 
 expiration of a definite period after the date of borrowing, as 
 provided by the library rules or by special arrangement with 
 the Librarian in charge. 
 
 DATE BORROWED 
 
 DATE DUE 
 
 DATE BORROWED 
 
 DATE DUE 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 C28 (747) MlOO 
 
 
 
 
^416 
 
 L81 
 
 Lockwood 
 
 Hunterian lectures on the devel- 
 opment & transition of the testis, 
 normal and abnormal . 
 
 QM^/C' 
 
 L^l