446 Profs. A. Alcock and L. Eogers. On the Toxic [Apr. 28, 



" On the Toxic Properties of the Saliva of Certain ' Non-poisonous' 

 Colubrines." By A. Alcock, M.E., LL.D., F.K.S., Professor of 

 Zoology, and Leonard Eogees, M.D., B.S. (Lond.), M.E.C.P., 

 F.B.C.S., Officiating Professor of Pathology in the Medical 

 College of Bengal. Eeceived April 28, — Eead June 12, 

 1902. 



CONTENTS. 



I. General Statement and Conclusions. 

 II. Details of Experiments. 



A. With Opisthoglyphous Combrines. 



B. With Aglyphous Colubrines. 



III. Tabulated Summary of Experiments. 



I. General Statement and Conclusions. 



Although numerous elaborate experiments, directed chiefly towards 

 practical ends, have been made to determine the physiological effects 

 of the parotid secretion of those Colubrine snakes whose bite is fatal 

 to man, yet very little seems to have been done, by studying the effects 

 of the saliva of the non-poisonous Colubrines, to assist us in forming 

 some opinion as to how, on the theory of gradual modification by 

 means of natural selection, the efficient lethal mechanism of the 

 poisonous Colubrines may be supposed to have originated and become 

 gradually perfected in all its parts. 



On comparing two strong, active reptiles like the common Cobra 

 (Naia trijmdians) and the common Eat-snake (Zamenis mucosas) of this 

 country, both of which seem to lead — and with identical success — 

 lives that are essentially similar, two perplexing questions occur. 

 The first question is — what is the manifest advantage to the Cobra, 

 over the Eat-snake, of its venom 1 The second is, admitting that there 

 must be some advantage — is it conceivable that it can be founded on 

 any fundamental and unbridgecl difference in the nature of the saliva 

 of trie two species ? 



A few experiments that we have made seem to point to the con- 

 clusion that the difference is not a radical one but is only one of 

 degree, and that the parotid secretion of some of the "harmless" 

 Colubrines is to a certain extent poisonous when injected subcu- 

 taneously. 



That the poison-gland of the venomous snakes is merely a modified 



