DESCENT OF THE TESTES. 1161 



to or just within the margins of the sinus (verumontanum). The ducts diminish in 

 size and converge toward their termination. 



Structure. The vesiculae seminales are composed of three coats : an external 

 or libra-cellular; a middle or muscular coat, which is thinner than in the vas 

 deferens : the muscular fibres are arranged in three layers, consisting of an inner 

 and outer longitudinal stratum and an intermediate layer of circular fibres ; and 

 an inter tu'd or mucous coat, which is pale, of a whitish-brown color, and presents 

 a delicate reticular structure, like that seen in the gall-bladder, but the meshes are 

 finer. The epithelium is columnar. 



The coats of the ejaculatory ducts are extremely thin. They are: an outer 

 fibrous layer, which is almost entirely lost after their entrance into the prostate; 

 a J'ii/er f muscular fibres, consisting of an outer thin circular and an inner 

 longitudinal layer; and the mucous membrane, forming the only constituents of 

 the tubes. 



Vessels and Nerves. The arteries supplying the vesiculse seminales are derived 

 from the middle and inferior vesical and middle hsemorrhoidal. The veins and 

 lymphatics accompany the arteries. The nerves are derived from the pelvic 

 j ilex us. 



Surgical Anatomy. The vesiculae seminales are often the seat of an extension of the 

 <lisoa>f in ru-es of tuberculous disease of the testicle, and should always be examined from the 

 rectum before coming to a decision with regard to castration in this affection. 



Descent of the Testes. 



The testes at an early period of foetal life are placed at the back part of the 

 abdominal cavity, behind the peritoneum, in front and a little below the kidneys. 

 The anterior surface and sides are invested by peritoneum. At about the third 

 month of infra-uterine life a peculiar structure, the gubernaculum testis, makes its 

 appearance. This structure is at first a slender band which extends from the 

 situation of the internal ring to the epididymis and body of the testicle, and is 

 then continued upward in front of the kidney toward the Diaphragm. As 

 development advances the peritoneum covering the testicle encloses it and forms 

 a mesentery, the mesorchium, which also encloses the gubernaculum and forms two 

 folds one above the testicle, and the other below it. The one above the testicle is 

 the plica vascularis, and contains ultimately the spermatic vessels; the one below, 

 the plica yubernatrix. contains the lower part of the gubernaculum, which has now 

 grown into a thick cord ; it terminates below at the internal ring in a tube of peri- 

 toneum, the processus vaginalis, which now lies in the inguinal canal. The lower 

 part of the gubernaculum by the fifth month has become a thick cord, whilst the 

 upper part has disappeared. The lower part can now be seen to consist of a central 

 core of unstriped muscle-fibre, and outside this of a firm layer of striped elements, 

 connected, behind the peritoneum, with the abdominal wall. Later on, about 

 the sixth month, the lower end of the gub ernaculum can be traced into the inguinal 

 canal, extending to the pubes, and, at a later period, to the bottom of the scro- 

 tum. The fold of peritoneum constituting the processus raginalis projects itself 

 downward into the inguinal canal, forming a gradually elongating depression or 

 cul-de-sac, which eventually reaches the bottom of the scrotum. This cul-de- 

 sac is now invaginated by the testicle, as the body of the foetus grows, for the 

 gubernaculum does not grow commensurately with the growth of other parts, and 

 therefore the testicle, being attached by the gubernaculum to the bottom of the 

 scrotum, is prevented from rising as the body grows, and is drawn first into the 

 inguinal canal, and eventually into the scrotum. By the eighth month the 

 testicle has reached the scrotum, preceded by the lengthened pouch of peritoneum, 

 the processus vaginalis, which communicates by its upper extremity with the per- 

 itoneal cavity. Just before birth the upper part of the pouch usually becomes 

 closed, and this obliteration extends gradually downward to within a short dis- 

 tance of the testis. The process of peritoneum surrounding the testis, which is 



