60 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 
gland. Its anatomical position corresponds with that of the parotid gland 
of the Mammalia, to which its similarity is still further strengthened by the 
serous character of the secretion. A certain digestive function of the poison 
gland has been described and is alleged to be essential to digest the prey. 
The venom gland like the parotid gland has only one excretory duct. Allu- 
sion has been made to the fact that the secretion of the poison gland has a 
double importance to the reptile —to assist digestion and to capture prey. 
The dimension! of the poison glands is generally in proportion to the size of 
the snakes, although some exceptions are observed in certain species. Of 
the Crotalidz with the length of about 5 feet the gland attains the size of an 
almond. ‘The cobra is provided with a somewhat larger gland. The Euro- 
pean vipers have much smaller glands, as their size is not very great. It is 
a curious fact that the genus Doliophis, one of the venomous colubrine genera, 
is characterized by the possession of a very large, elongated poison gland 
which extends down one-third of the entire length of the body. It ends in a 
club form in front of the heart, shifting the latter to the right. Especially 
Doliophis ? intestinalis and Doliophis bivirigatus are noted for their enormous 
glands. In the visceral region the glands are in one mass and separate from 
one another near the head in order to supply the poison fang on each side. 
Similar glands are described by Meyer in Doliophis philippinus, Doliophis 
nigroteniatus, and Doliophis flaviceps. 
The gland is surrounded by striated muscle fibers which run parallel to its 
longitudinal axis. According to Meyer and Hoffmann (1890) another duct 
opens near the exit from a second large gland which lies behind the eye. In 
Causus rhombeatus Reinhardt discovered a poison gland disproportionately 
large. In a specimen which measured 18 inches the gland with the duct 
reached 3 inches. The gland runs down along each side and lies on the ribs 
and muscles, and is provided with a muscle attached to it. 
The poison gland is for the most part a serous gland. A considerable 
variation is noted in the structure of poison glands throughout Ophidia. In 
proteroglyphous colubrine snakes the alveoli of the gland are much larger and 
have a lining epithelium of short columnar cells inclosing a capacious lumen 
in which secretion is stored. The supporting framework of interalveolar 


1S. Weir Mitchell gives the following measurements for the Crotalus adamanteus kept two to eight 
weeks in captivity: 

No. Weight. Length. Meee oe 
1 lb. 6 oz. ft. x inch 7} grains 

2 Meyer, the discoverer of this visceral poison gland, used the term Calliophis or Callophis, but Wil- 
helm Peters (1871) devised a special generic name Adeniophis for this particular group. Bou- 
lenger again employed the third name Doliophis in lieu of Peters’s Adeniophis. 
