1903.] Action of the Poison of t lie Hydrophidcc. 487 



kill a fish as is sufficient to kill a warm-blooded animal — a very marked 

 difference. On testing the same species of fish with the poison of the 

 Enhydrina, it was found that 0*5 milligramme per kilo of freshly dis- 

 solved poison was always fatal, and sometimes a smaller dose caused 

 death. Thus the dose of this sea-snake poison required to kill fish 

 was but ten times as much as the minimal fatal dose for warm-blooded 

 animals, that is, considerably less than we found to be the ease with 

 Cobra poison. In other words, the poison of the Enhydrina is much 

 more deadly than is Cobra venom for fish, even allowing for the 

 greater potency of the former for warm-blooded animals, so that it 

 appears to be specially adapted for the needs of the Sea-snake, which 

 lives on fish, being in all about fifty times as potent for fish as is Cobra 

 venom. This great concentration of the poison may be of considerable 

 advantage to the reptile when dealing with such active prey as fish in 

 their own element. This special affinity of the poison for fish was even 

 more marked in the case of some of the other species tested. Thus, 

 that of a single species of the Disteira cyanocincta was fatal to pigeons 

 in doses of 0*5 milligramme per kilo, being thus considerably weaker 

 than that of the Enhydrina, but only 1 milligramme per kilo was 

 required to kill fish, that is but twice as much as was needed to kill 

 birds. Similarly with the Disteira viperina the minimal lethal dose for 

 pigeons was 0'5 milligramme, and for fish only 0*75, or but very little 

 more. Again, the poison of the Hydrophis cantoris for both pigeons 

 and fish was just the same as the last-mentioned species. Lastly, the 

 poison of the Hydrus platurus killed pigeons in doses of 0*075 and fish 

 in one of 0*25 milligramme per kilo, being thus very deadly for both 

 cold and warm blooded animals. The above include four out of 

 the six genera of Hydrophidse found in Indian waters, so that, 

 although the poison obtained from the last four species was from 

 single specimens, and therefore cannot be taken as more than approxi- 

 mately accurate, yet they suffice to prove that the Hydrophidae as a 

 class secrete very virulent poisons, which are specially poisonous to 

 fish. It is also worthy of note that the two genera which proved to 

 be most deadly to warm-blooded animals, namely, the Enhydrina and 

 the Hydrus platurus, are just the two which the fishermen at Puri 

 said were the most dangerous ones, as the accuracy of their statement 

 points to actual experience in the human subject of their deadliness 

 having been handed down among them. Some of the smaller species, 

 however, probably do not eject sufficient poison to prove fatal, 

 to adults at any rate, and hence are not so much dreaded by the 

 fishermen. It will also be observed that the poison of the Enhydrina 

 Bengalensis is the most potent of those so far tested, while it also yields 

 the greatest amount of poison, with the exception, perhaps, of the 

 Disteira cya n ocincta . 



