196 RESEARCH IN PROTOZOOLOGY 



not been obtained. Their investigation is being continued in 

 various laboratories. 



FACTORS THAT COMPLICATE EXPERIMENTS WITH KITTENS 



The animal body is adapted to combat disease since parasitism 

 has no doubt occurred throughout the course of evolution. Further- 

 more, the body responds in a typical manner to the attack of a 

 given parasite; hence diagnosis may be made from symptoms. 

 The ideal of the experimental method is to study the effects of 

 transmission of a given parasite to healthy animals, i.e., those that 

 are free from other pathogenic parasites and live under conditions 

 that are conducive to their well being. These effects should be 

 compared with those that occur in controls. Even so, the inter- 

 play of many unknown factors makes it necessary to repeat the 

 experiments a number of times before much dependence can be 

 placed on them. Unlike rats, mice, and guinea-pigs, cats are not 

 commonly reared in the laboratory. They are taken from an en- 

 vironment in which they were free to roam and isolated in wire 

 cages. Furthermore, the food that they receive is seldom the same 

 as that which they selected before capture. The above factors 

 affect them unfavorably. This is particularly true of kittens of 

 the age susceptible to amoebiasis. Intercurrent infections such as 

 pneumonia and bacillary dysentery, which would otherwise be held 

 in check, may appear. The kittens are usually purchased from 

 the streets; some come from alleys, others from sections where 

 living conditions are more favorable. Kittens in different parts of 

 the world are subject to different endemic infections which makes 

 it difficult to compare results of different laboratories. It will 

 be shown in following paragraphs how some of these complicating 

 factors may be evaluated, but it is obvious that careful studies of 

 the needs and habits of kittens should be continued in order that 

 experiments with them may be placed on a par with those in 

 which rats, mice, guinea-pigs and other laboratory animals have 

 been used. 



SELECTION AND CARE OF KITTENS 



Very few kittens are obtainable during the winter months and 

 laboratory conditions are very unfavorable during this season. It 

 is, therefore, advisable to plan the experiments so that a given 

 series may be completed in early autumn. The animal room should 

 be well lighted so that kittens may enjoy direct sunlight during 



