TKOPIDONOTUS. 245 
COLUBETDiE. 
Series A. A GLYPH A. 
COLUBRINM \ 
TROPIDONOTUS. 
Tropidonotus, Kuhl, in Ferussac, Bull. Sc. Nat. ii. 1824, p. 81. 
Body cylindrical, elongate ; head flattened, distinct from the neck ; tail elongate ; 
nostril between two plates ; a loreal always present ; head-shields regular ; eye 
moderate, large, or rarely small ; pupil round. Body-scales usually with apical pits, 
ovately lanceolate, imbricate, carinate, rarely smooth, in longitudinal series ; ventrals 
broad, rounded ; subcaudals divided ; anal entire or divided ; maxillary, palatine, and 
mandibular teeth present, the maxillary teeth short anteriorly, long posteriorly. 
Until within the last few years it was not known that the members of this genus 
were possessed of a poisonous secretion for the destruction of their prey ; but, so long 
ago as 1787, Fontana stated that they were immune to the bite of the viper and to 
the subcutaneous injection of its poison 2 . MM. Phisalix and Bertrand 3 have fully 
verified this assertion, as they injected a small example of T. natrix (50 cm. long) with 
0"005 gr. of dry venom of the viper, a dose capable of destroying 15 to 20 guinea-pigs, 
but which had no effect on the snake. They then set themselves to discover the cause 
of this immunity. After the explanation they had already given of the immunity 
enjoyed by the toad and viper to their own poisons, it seemed to them rational to 
search in the blood of Tropidonotus for toxic substances analogous to echidnine. 
They accordingly extracted antiseptically, under the influence of chloroform, blood 
from the hearts of T. natrix and T. viperinus, two species closely allied to T. tessellatus, 
and injected very minute quantities either of the serum only or of the blood itself into 
the peritoneal cavity of guinea-pigs, with the invariable result that death ensued in 
little more than two hours, preceded by all the symptoms attending poisoning by the 
blood or venom of the viper. To ascertain the source of this poison in the blood of 
these snakes, they attempted to discover it by the successive inoculation of guinea- 
pigs with organic extracts of the principal viscera — liver, pancreas, spleen, thymus, 
thyroid body, and salivary glands. Injections of preparations of the first five of these 
organs into the peritoneal cavity had no evil effect. This, however, was not the 
case with the injection of the liquid extract of the salivary glands (superior 
1 Blgr. Faun. Brit. Ind., Eept. 1890, p. 279. 
2 It seems to be established that venomous serpents are protected against their own venom, but it does 
not appear that they are immune to the venom of snakes generically distiuct from themselves. Mr. Thomson, 
Head-Keeper of the Zoological Gardens, informs me of two cases that illustrate this — the first in which Elaps 
fulvus killed Vipera berus and Lachesis atrox, and the second in which Bungarus fasciatus destroyed by its 
bite Diemenia nuchalis. 3 C. E. Ac. Sc. 1894, pp. 76-79. 
