EFFECTS OF CHANGES IN THE DIET 109 



In the studies on trichomonads, an attempt was made to enu- 

 merate (i) the lactose-fermenting organisms, (2) the aciduric 

 bacteria and (3) the anaerobic bacteria. Lactose-litmus-agar was 

 employed in plate counts of the first group, and tomato juice- 

 peptone agar (Kulp, 1927) in plate counts of the second group. 

 Dilution counts were made of the anaerobes in cooked meat me- 

 dium (Kahn, 1922). The intestinal material was diluted to an ex- 

 tent found to be appropriate and one cubic centimeter amounts 

 planted in these media. Kendall's Bacteriology and A Treatise on 

 the Transformation of the Intestinal Flora (Rettger and Cheplin), 

 1921) will be helpful in understanding the bacteria involved. 

 Ford's Text-book of Bacteriology describes the preparation of 

 media. 



It seems essential in understanding the influence of food on 

 the intestinal protozoa of any animal tliat similar observations 

 be made. 



2. Diets and Experimental Animals. Diets must contain all sub- 

 stances necessary for growth and reproduction of experimental 

 animals, and all ingredients should be thoroughly mixed. Labora- 

 tory rats are well standardized, and it is possible to alter their food 

 so that their intestinal conditions may be made to simulate those 

 of other animals. The writer (Ratcliffe, 1928) published a list 

 of diets, planned by the Department of Chemical Hygiene of this 

 school, that are known to" produce a variety of conditions in the 

 intestine of VaXs. It is probable that these diets could be used 

 with mice or guinea-pigs, but experiments would be necessary to 

 determine this. 



Diets for other laboratory animals, with the exception of the 

 domestic fowl, have not been standardized satisfactorily to allow 

 experimental observations comparable to those possible with rats. 

 With chicks it is possible to procure satisfactory food mixtures in 

 a dry form, but the degree of modification possible with the 

 diets has not been determined so far as is known to the writer. 

 Neither is it possible to remove samples from the intestine of 

 chicks by surgical methods. However, Dr. Robert Hegner has 

 found that intestinal protozoa of chicks live in the ceca, and that 

 material is passed from this portion of the intestine separately 

 and is different in color from material passed from the colon. 

 This allows one to obtain material closely approxima<"ing that 

 in which the protozoa live. Hence it is possible to make observa- 



