PHYLOGENY OF VENOMOUS SNAKES 47 
the poisonous to the non-poisonous species. The question may be raised as 
to whether the poison gland and fang came into existence at the same time, 
or whether one antedates the other. If not of simultaneous appearance, 
which of the two came first? Through elaborate work of various investiga- 
tors it was made clear that the poison gland does exist in the group of snakes 
which possesses no grooved or perforated teeth, and the presence of the 
grooved tooth is always associated with a much more developed venom gland 
than the rudimentary form of the aglyphous species. The poison gland of the 
snake is a modified form of the glandula labialis superior and in all probability 
is equivalent to, if not identical with, the parotid of the mammalia. 
In the Urodelia and the Anura the oral cavity is provided with the mucus- 
secreting glands which are located in the internasal and lingual regions, and 
also in the pharyngeal area in the latter order. In the Chelonia the medial 
and lateral palatine glands take the place of the internasal, and the sub- 
lingual appears anew. In the Crocodilia no sublingual gland is present. 
First in the Sauria, comprising both the Lacertia and the Ophidia, the glan- 
dula labialis, superior and inferior, are added to the sets already mentioned. 
For the Ophidia no palatine gland is present, but there is sometimes the 
poison gland. Phylogenetically considered, the salivary glands appear first 
in the Amphibia, in which the mucus-secreting glands are the only kind. 
In the Pisces no salivary gland is found. The majority of the Reptilia 
possess the mucous gland with a fairly high, clear cylindrical epithelium, 
which contains more or less granules in the protoplasm (Wiedersheim, 
1886). In this class, however, not only the number of glands, but also their 
shape, arrangement and structure, become more abundant and variable, with 
acquisition of certain new functions at the same time. In certain Sauria, for 
example, the Lacertia and Anguis fragilis, a serous and a mucous gland are 
formed in the area of the sublingual gland, a fact which shows that the con- 
dition is gradually approaching the mammalian class. 
The poison gland of snakes has occupied the minds of many great anato- 
mists for solution of its origin and its relation to the salivary glands, both in 
the same order and in the orders next to it. Comparative studies of Carus 
(1834), Tiedemann (1810), Meckel (1829), Stannius (1846), Ellenberger 
and Hoffmeister (1881), and others demonstrated that in the mouth of birds 
of prey there are at least four to five sets of glands, corresponding to the sub- 
maxillary, sublingual, lingual, parotid, and a group of glands (follicle) near 
the side of and behind the posterior nostrils, which, together with a large 
group around the Eustachian tube, was held for the tonsils by Rapp (1843). 
Rapp’s interpretation was shown to be incorrect by the work of Kahlbaum 
(1854), Leydig (1857), Stéhr (1884), Gadow (1891). The peculiarity of the 
avian mouth is in the presence of a ‘pair of glands over the maxillary joint. 
Carus (1834) was not able to decide whether it is to be considered an analogue 
of the parotid of the mammalians or the poison gland of snakes. Ranvier 
(1884, 1887) held that the cells of the gland erroneously called the submaxil- 
laris are mucus-secreting, which is not the case with the gland of the labial 
commissure. Battelli and Giacomini (1889) described two types of cells, 
