258 THE VISCERA, 
The Scrotum and Testes, 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. 111, @) 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: 
1. The scrotum (the integument). 
