no RESEARCH IN PROTOZOOLOGY 



tions on intestinal protozoa of chicks similar to those on rats, 

 provided diets can be planned successfully. 



With the exception of laboratory rats and chicks other labora- 

 tory animals must be standardized before it will be possible to em- 

 ploy them in anything but the crudest type of experiments. 



PROBLEMS 



1. Natural Infections. By natural infection is meant infection 

 with intestinal protozoa that is acquired by the young from the 

 mother. 



a. The relation of all intestinal protozoa of rats or fowls to 

 changes in diets may be studied by the methods described above. 



b. A more detailed study of changes in intestinal flora accom- 

 panying changes in diet may lead to a better understanding of 

 the problem and determine the effects of bacteria due to numbers 

 as well as effects due to metabolic products. 



2. Cross-infection. Parasite-free animals must first be obtained 

 before work of this nature can be attempted. Chicks, of course, 

 are readily available, while a breeding stock of parasite-free rats 

 may be established by the following method. 



Since young rats become infected with intestinal protozoa from 

 the mother while they are being weaned and are beginning to eat 

 solid food, young may be taken from the mother soon after the 

 eyes are open, fifteen to twenty days after birth, and reared to 

 maturity free from intestinal protozoa, provided food is not 

 allowed to become contaminated and contact with infected animals 

 is prevented. 



The chief difficulty will be encountered in inducing the young 

 animals to eat. Whole milk powder dissolved in warm water may 

 be fed for the first day or two. It is usually necessary at first to 

 give the milk to each animal separately by means of a pipette. 

 Dry food, green vegetables and water may be given after the 

 second day, the food and water being placed in shallow vessels 

 in the cage. 



About two-thirds of the young may be expected to survive this 

 treatment, but once a breeding stock of parasite-free rats has 

 been established animals can be reared in the usual way. 



The following problems are suggested : 



a. Cross-infection experiments will allow a study of the relation 

 of diet to specificity of parasites. 



