1903.] 



Action of the Poison of the H ydrophidce. 



485 



lasting for several hours. Sometimes temporary excitement with 

 rapid motion may he ohserved for a short time, but more often the 

 picture is simply one of slowly progressing paralysis. In most kinds 

 of fish this is also very well shown by a gradually increasing difficulty 

 in maintaining the upright position, the fish slowly turning over on 

 one side and then swimming up into its upright position again, only 

 to slowly sink on to its side once more. The respirations will now 

 he found to be deeper than normal, although not as a rule quicker, 

 but, on the contrary, they steadily slow down from the beginning of 

 the symptoms to the end without any marked increase in the rate. 

 This paralysis of all the muscles and of the respirations steadily 

 progresses until convulsions set in, to be immediately followed by a 

 very rapid failure of the respirations both in number and depth, so 

 that they become difficult to detect, and death soon follows. The 

 heart will be found beating some time after the breathing has ceased, 

 and no extravasation of blood or other noteworthy change is found 

 post mortem. Here again the symptoms are precisely similar in 

 poisoning of fish by Cobra venom. 



The Potency of the Poison. 



By working out the smallest fatal doses of the poison per kilogramme 

 of weight in different animals, and comparing them with those obtained 

 by former workers for other snake venoms, we shall be able to esti- 

 mate the potency of that now being dealt with. This has been done 

 in the case of the poison of the Enhycliina by means of numerous 

 experiments carried out with the mixed dried venom of a number of 

 these snakes, with the following results, At the same time com- 

 parative experiments were also carried out with fresh dried Cobra 

 venom for comparative purposes. White rats were first tested, and 

 0*07 milligramme per kilo weight was found to prove fatal, but 

 smaller doses were sometimes recovered from. In the case of Cobra 

 poison 0*5 milligramme per kilo was necessary to produce death, 

 while Lamb in Bombay found the fatal dose of this poison for rats 

 to be 0-33 milligramme. It is evident then that the poison of the 

 Enhydrina is several times as potent as is Cobra venom on rats. 

 In the case of rabbits only a few experiments have been performed, 

 but O01 milligramme per kilo proved fatal in under four hours in 

 one case, while in another 0*01 milligramme per kilo produced no 

 symptoms but loss of appetite ; but on giving a second dose of 

 O02 milligramme per kilo five days later (the animal having fully 

 recovered from the first dose in one day), death resulted in a few 

 hours. On the other hand, Elliot found the minimal lethal dose 

 of Cobra venom for rabbits to be 0'7 milligramme per kilo weight, 

 so that it is evident that these animals are many times as suscep- 



