258 THE VISCERA. 



The Scrotum and Tcstes, and the Ducts of the Testes. The 

 scrotum contains the two testes, one in each of its compart- 

 ments. Each testis lies in a diverticulum of the abdominal 

 cavity, which is lined by an extension of the peritoneum. 

 The testis has the same relation to this peritoneal diverticulum 

 that the intestine has to the abdominal cavity; i.e., it does not 

 lie within the cavity of the diverticulum, but is suspended 

 apparently within it by means of a fold of its wall which acts 

 as a mesentery. The peritoneal diverticulum is called the 

 tunica vaginalis propria and consists thus of a parietal layer 

 and a visceral layer. 



The tunica vaginalis propria consists of a slender proximal 

 part through which the blood-vessels pass to the testis and the 

 vas deferens from it, and of an expanded distal part in which 

 lies the testis. Only the distal part lies within the scrotum. 

 The blood-vessels and vas deferens are suspended in the narrow 

 part of the tunica vaginalis propria by means of a mesenterial 

 fold similar to that which suspends the testis, and continuous 

 with it. This fold and the blood-vessels and vas deferens con- 

 tained within it form the spermatic cord (Fig. 1 1 1 , d} which 

 passes from the abdomen to the scrotal sac in the narrow part 

 of the tunica vaginalis propria. In the formation of the human 

 tunica vaginalis the various layers of the body wall are carried 

 out by it and form the tunics, or coats of the testis. The one 

 of these coats next the tunica vaginalis propria (which is 

 reckoned as one of the coats) is the tunica vaginalis communis 

 (or fascia propria) and is formed by the transversalis fascia. 

 Outside of the tunica vaginalis communis is the cremaster 

 muscle, an incomplete layer formed from the fibres of the 

 internal oblique muscle. Next is the cremasteric (or inter- 

 COlumnar) fascia from the aponeurosis of the external oblique 

 muscle, and outside of this is the integument forming the 

 scrotum. In this integument there is a layer of smooth muscle 

 which is sometimes described as the tunica dartos. In the cat 

 the tunica dartos and the cremaster muscle are wanting. The 

 cremaster is replaced by the elevator scroti muscle. The coats 

 of the testis are thus five, as follows: 



i. The scrotum (the integument). 



