486 



Dr. L. Rogers. On the Physiological 



[Mar. 31, 



tible to the poison of Enhydrina as to that of Cobra, the former 

 poison being some twenty times as potent for them as the latter — 

 a remarkable difference. 



A larger number of experiments have been carried out with 

 birds, pigeons and fowls. These also bear out the former ones in 

 proving the far greater potency of the poison of the Enhydrina 

 over that of the Cobra or other poisonous snake yet examined. In 

 the case of pigeons the minimal lethal dose, 0*05 milligramme per 

 kilogramme, always proves fatal, while in fowls the fatal dose is O04. 

 These figures may be compared with those obtained by D. D. Cun- 

 ningham in his numerous experiments with Cobra venom on fowls, 

 for which he found the minimal lethal dose to be 0*5 milligramme 

 per kilo, so that the poison of the Enhydrina for birds is at least ten 

 times as potent as is Cobra venom, which goes far towards neutralising 

 the effect of the much smaller dose of poison ejected by the Enhy- 

 drina as compared with the Cobra. Taking the minimal lethal dose of 

 the Enhydrina for warm-blooded animals as 0"05 milligramme per kilo, 

 the fatal dose for an average man of 70 kilogrammes would be 

 3*5 milligrammes, or about one-third of the average amount of venom 

 ejected by a fresh full-grown specimen of this, by far the most com- 

 monly met with, kind of snake in the Bay of Bengal. There is good 

 ground, then, for the belief in the deadliness of the Hydrophidae. 



The Minimal Lethal Dose for Fish. 



It is well known that it is necessary to give many times as large a 

 dose of Cobra venom, in proportion to the weight of the animal, in 

 order to kill cold-blooded animals as is required for destroying the life 

 of warm-blooded animals. Xow there is no doubt that the Enhydrina 

 live on fish, and I have been able to ascertain that they can swallow 

 those of considerable size. One specimen of Enhydrina after being- 

 handled in the process of taking poison vomited a piece of half- 

 digested fish, which on comparison with complete fish of the same kind 

 was found tc have certainly been a foot or more in length, while it 

 was over 2 inches in depth. Such a fish could not have been swallowed 

 if it had not first been killed, or at least paralysed to a marked 

 degree. It is of interest, then, to ascertain the minimal lethal dose of 

 these snakes against fish, and to compare it with that of the Cobra. 

 As I have not been able to find accurate records of the effect of 

 Cobra venom on fish, I have also ascertained this by a series of 

 experiments, using the hardy Mud-fish (Saccobranchus fossil is), which 

 lives for weeks in a small "vessel of water. It was found that 

 25 milligrammes per kilo of Cobra venom had to be given to be 

 certain of causing death, although sometimes a slightly smaller dose 

 was effective. Thus fifty times as much Cobra venom is required to 



