The Urinogenital System. 197 



from the transverse muscle. It is supplied with blood from the 

 external spermatic artery. Make a longitudinal incision through 

 this muscle, cutting forward into the abdominal cavity. On 

 spreading apart the two flaps the following features may be made out : 



(a) The parietal layer (lamina parietalis) of the tunica 

 vaginalis propria, a layer of peritoneum, continuous with 

 that of the abdominal wall, forms the internal lining of the 

 sac of the testis (cf. p. 100 and Fig. 55). The sac is widely 

 open to the abdominal cavity so that the testis passes 

 freely from one cavity to the other. 



(b) The male reproductive gland,- the testis, with its associated 

 vessels and duct, occupy the cavity of the sac, the testis 

 being suspended from its dorsal wall. 



(c) The gubernaculum, a short thick cord containing smooth 

 muscle fibres, joins the posterior epd of the testis with the 

 end of the sac. 



(d) The visceral layer (lamina visceralis) of the tunica 

 vaginalis propria forms the peritoneal coat of the testis and 

 is continuous with the mesorchium, a broad vertical fold of 

 peritoneum connecting the testis dorsally and anteriorly with 

 that of the body-wall. 



(e) The first portion of the duct of the testis, the epididymis, 

 usually imbedded in fat, forms a thickened mass at the an- 

 terior end of the testis, and extends backward as a thinner 

 cord along its side. The thickened anterior portion is the 

 caput epididymidis and the contracted posterior portion, 

 the Cauda epididymidis. The second portion, the ductus 

 deferens, leaves the testis at its posterior end, where it is 

 firmly attached to the gubernaculum. The connection 

 with, the epididymis may be shown by carefully separating 

 the duct from the gubernaculum and the side of the testis. 

 The ductus deferens receives its blood supply from the 

 umbilical artery. 



(f) The internal spermatic artery (a. spermatica interna) 

 arises from the abdominal aorta, in the neighbourhood of the 

 inferior mesenteric artery, or opposite the sixth lumbar 

 vertebra, the left artery usually behind the right. It enters 

 the anterior end of the testis. 



