84 ESSAY ON THE DESCRIPTIVE ANATOMY OF THE 
This tube, of very various length, is constituted of an outer 
cellular investment, not requiring peculiar notice; of an inter¬ 
mediate contractile and elastic tunic; and, as its name implies, is 
composed of muscular fibres and elastic tissue, arranged in two 
layers, i.e. an outer longitudinal and an inner circular one, which 
are easily perceived. 
The internal or mucous lining is thrown into longitudinal folds, 
in the narrow part of the duct; but in the bulbous part it forms 
permanent rugse, taking various directions, so as to enclose 
irregular interspaces. 
The vas deferens is supplied with blood principally from the 
artery of the cord, although the epigastric furnishes a twig to 
it as well. The bulbous portion is supplied also by vessels 
of no small caliber from the iliacs. 
Its nerves are from the sympathetic, as well as from the 
second and third lumbar. 
Vesiculce Seminales. 
The seminal vesicles are one on each side of the bladder, and 
act as receptacles for the semen. 
Each seminal vesicle extends from behind forwards, upwards, 
and outwards, being external to the bulbous portion of the vas 
deferens. It is attached by peritoneum coming off from the 
sides of the pelvis and rectum on to the bladder. The posterior 
part is fixed by cellular tissue to the prostate and neck of the 
bladder. 
The seminal vesicle is pyriform, being about three inches 
long and about an inch broad at its fundus, but more constricted 
at its neck. It is connected with the corresponding surface of 
the bladder and rectum, but partially separated from the latter 
by the prostate. 
The seminal vesicle has an incomplete investment of peri¬ 
toneum, covering only the anterior part, whilst the prostatic por¬ 
tion is covered by an outer cellular coat. Beneath this is an 
intermediate tunic partly elastic and partly contractile. Lavocat 
describes this muscular coat as easily studied after maceration 
in dilute nitric acid, when it may be found to consist of an outer 
longitudinal and inner circular layer, most developed at the 
fundus, but very thin at the neck. 
The mucous membrane is plicated, the folds enclosing similar 
interspacesto those seen in the bulbous portion of the vas deferens. 
The vessels are supplied by the internal pudic, whilst the 
perves are from the lesser splanchnic and two last sacral pairs. 
