POISON APPARATUS OF VENOMOUS SNAKES 59 
In the opisthoglyphous snakes the fangs are short and have usually much 
shallower furrows than the proteroglypha. The fangs differ greatly in their 
magnitude according to the snakes. The viperine and crotaline snakes pos- 
sess the best-developed and longest fangs, while the elapine and hydrophine 
families have much shorter ones. A fang an inch long is not uncommon in 
Crotalus and Lachesis. It is hardly necessary to mention that the poison 
fangs are provided with a regular pulp-cavity which occupies a space just 
behind the groove or canal separated with a thin septum of dentine and 
enamel. 
The relation of the poison duct to the fang has often been misinterpreted. 
Niemann! even reproduced a picture in which the poison duct was shown to 
enter directly into the base-opening of the canal of the fang. But Mitchell 
as early as 1860 described the real method by which the poison duct communi- 
cates with the groove of the poison fang. It is by means of the cavity sur- 
rounding the base of the tooth and inclosed by the mucous membrane folds 
which constitute the proximal portion of the vagina dentis. In Crotalus 
Mitchell discovered the presence of certain muscular fibrillze in the mucous- 
membrane sheath, which apparently serves as a sphincter. ‘This arrangement 
has the advantage that in the replacement of the fang the connection will 
not in any way be affected, in spite of the change of the position of a new 
fang. The sphincter which has been found by Mitchell near the termination 
of the duct in the Crotaline appears to be absent from the proteroglyphous 
Colubrinz, while in Hydrophiine a non-striated muscle is present near the 
base of the fang. 
POISON GLANDS. 
(Plate 20, A, B, C, D.) 
Glandula venenata were not definitely discovered until a correct account 
was given by Fontana. Schlegel (1828) found in many snakes with furrowed 
posterior teeth a large gland which opens its duct only at the base of this tooth. 
Duvernoy (1832) then found that a similar gland exists also in numerous sus- 
pected snakes. The poison gland of fangless snakes is not exactly equal to 
the fully developed venom gland of fang-possessing reptiles, but is a mixed 
gland, consisting of anterior grayish-red portion and posterior grayish-white 
portion. The latter is provided with only one duct. After the careful studies 
of Rudolphi, Meckel, and Leydig (1873) it became clear that the posterior 
portion is of the nature of a serous gland, while the anterior portion is that 
of a mucous gland. It is noteworthy that a serous gland comes for the first 
time into existence in these snakes, but not in any class in the inferior evolu- 
tional order, which, as in Amphibia, is provided with a mucous gland. In 
the Mammalia the existence of the serous gland becomes universal. 
In the majority of venomous snakes the poison gland occupies a space 
behind the eye and stretches backwards in length according to the size of the 
eee 
1 Niemann, Arch. f. Naturgeschichte, 1892, I. 
