VIVIPAROUS ANIMALS. 393 
of the urethra, and usually on its dorsal aspect. Inter- 
nally it is cellular, and is destined to secrete a glairy albu- 
minous fluid. In many animals this gland is single, or 
the lobes of which it consists are attached to one another, 
and the secretion is poured into the urethra by numerous 
orifices. In other cases this organ consists of two, or even 
four separate glands, each having a common cavity, into 
which the different cells empty their contents, and a com- 
mon duct opening in the urethra. 
The organ in its simple form exists in man, the quad- 
ruma, and many other mammalia. It appears in the ele- 
phant and ruminating animals, in its most complicated 
form; while it is wanting in the hedgehog, mole, and 
many of the glires. 
Besides the seminal vesicles and prostate gland, there 
are two bodies which have been named, in honour of the 
discoverer, Cowper's Glands. 'These are situated immediate- 
ly behind the bulb of the urethra, with the walls of which 
they are intimately united. They differ greatly in tex- 
ture, and empty their contents into the urethra by a single 
duct. The fluid which they secrete is bluish-white, semi- 
transparent, and gelatinous. ‘They are surrounded by a 
muscular covering, which serves to expel their contents. 
In size and appearance they vary less with the season, 
than the two organs which have last been noticed. They 
are wanting in many mammalia, and, where present, exhi- 
bit many different combinations with the seminal vesicles, 
accessory vesicles, and prostate gland. 
The seminal fluid prepared in the testes, and conveyed 
through the spermatic duct, is thus finally mixed with the 
secretions of these assisting glands, and brought to its des- 
tination through the urethra. What are the properties of 
the seminal fluid itself? 
