826 PATHOGENICITY 



Trypanosoma leivisi. while older rats undergo a response to this micro- 

 organism, in behavior of leucocytes and monocytes, that confers on them 

 sufficient resistance for survival. 



Nutrition and Resistance 



Nutrition may have a far-reaching effect on physiological state, and 

 indirectly on resistance. The following hitherto-unpublished experiment 

 is useful in illustrating the point. Forty young rats of about fifty grams' 

 average weight were divided into two equal groups. One group was 

 fed the following mixture (parts by weight) : Beet sugar, 67; casein, 

 unextracted, 10; normal salt mixture, 3; lard, 3; cod liver oil, 2; bright 

 green alfalfa meal, 15. The other group was fed the same mixture, ex- 

 cept that alfalfa meal was replaced with whole oats ground to a fine 

 flour. After two weeks on these rations, the lot receiving the ground 

 oats had made slightly greater weight gains than the other. On the fif- 

 teenth to the eighteenth days each rat was fed 10,000 recently sporulated 

 oocysts of Ehneyja meschulzi, a coccidium that develops in enormous 

 numbers in the mucosa of the small intestine. On the sixth day the al- 

 falfa-fed rats were obviously affected with diarrhoea, while the oat-fed 

 animals were not showing distress. Strangely enough, on the seventh day 

 the alfalfa-fed lot appeared to be recovering, with formed stools and 

 return of appetite, but the oat-feds were off their feed and passing liquid 

 stools. On the eighth and ninth days, 16 out of 20 of the latter died, a 

 marked contrast to what happened in the alfalfa-fed lot all of which re- 

 covered. The result was rather surprising, in view of the biological assays 

 of Becker and Derbyshire (1937, 1938) and Becker and Waters 

 ( 1939a) , which showed that alfalfa meal in the ration in some manner or 

 other stimulated the development of several times as many oocysts of 

 Eimeria nieschulzi in its rat host as either oat hulls or hulled oats. 



What is the explanation of the observed effects.'' The early develop- 

 ment of diarrhoea in the alfalfa- feds appears to have been due to the 

 preponderance of the parasite population, but there is a possibility that 

 it lies in the superior accessory food factors of alfalfa meal. The follow- 

 ing experiment suggests that vitamin B may have had something to do 

 with it. Twenty young rats were fed the following ration: beet sugar, 

 71; soy-bean oil meal, expeller process, 10; casein, commercial medium 

 fineness, 10; normal salt mixture, 4; lard, 3; cod-liver oil, 2. Another 



