Ill 



ANIMALS STUDIED AND THE TECHNIC 



The animals used in these experiments rep- Methods 

 resent practically all animals. The most com- of study, 

 monly employed are sporozoa, fishes, frogs, 

 mosquitoes, mice, rats, guinea pigs, chickens, 

 pigeons, dogs, cats, cows, horses, monkeys, 

 apes, and men. The great majority of experi- 

 ments are in the nature of studies in the effects 

 of feeding and breeding under certain condi- 

 tions. These entail no operation or pain to 

 the animal. A lesser amount of experimenta- 

 tion is in studying the nature of diseases of ani- 

 mals. In some cases these diseases are found 

 naturally in the animal under observation, in 

 others the animal is purposely infected. A 

 lesser amount of work, but at the present time 

 the most fruitful that is being carried on, is the 

 inoculation of animals by the prick of a needle 

 with bacterial products for the purpose of de- 

 veloping in their blood certain substances which 

 are antagonistic to the bacteria. A still lesser, 



9 



