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) 
(b) 
(c) 
(d) 
(e) 
(f) 
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. 
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. 
The gubernaculum, a short thick cord containing smooth 
muscle fibres, joins the posterior end of the testis with the 
end of the sac. 
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. 
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. 
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. 
