POISONS AND THEIR PREVENTION 197 



perties are brought to light in a remarkable 

 manner in connection with the investigations 

 which have been carried out to artificially protect 

 animals from its lethal influence, and also in some 

 interesting experiments which have been made 

 to compare the toxicity of eel blood with that 

 of vipers. 



It is far from an easy matter to secure for 

 experimental purposes an adequate supply of eel 

 serum, for even a big fish weighing nearly five 

 pounds is not capable of yielding more than about 

 twenty-five cubic centimetres of blood, and from 

 this only from ten to twelve cubic centimetres 

 of serum are obtainable. Calmette has shown 

 that not only the venom glands of reptiles contain 

 toxic substances, but that the blood of such snakes 

 also possesses lethal properties, only in a far less 

 degree. Curiously, the serum of eels is no less 

 than three times as toxic as the serum of the 

 most vicious viper, and, moreover, produces far 

 more discomfort and pain to the animals into 

 which it is introduced than accompanies the 

 injection of viper blood. In the case of viper 

 blood its introduction is followed by no symptoms 

 of discomfort, the animal remains quite quiet, 

 growing more and more somnolent, a condition 

 which is followed by an abnormal fall of tempera- 

 ture, ultimately ending in complete collapse, 



