Dietary Conditions on Physiological Resistance. 63 



allowed to run at large in the laboratory for six months (July 17, 

 1906, to Jan. 10, 1907), no effort being made to collect excretions 

 for analyses. During this time the protein content of the diet was 

 gradually dropped to an equivalent of 0.27 gram of N per kilo. 

 The animal was painfully thin but appeared to be in excellent 

 health. She was lively during the warm months of summer and 

 autumn, but with the advent of colder weather she became less 

 and less active and lost weight, although the laboratory was 

 adequately heated. It finally became evident that the diet must 

 be changed. The portion of meat in the diet was gradually in- 

 creased, but a diarrhea supervened, which proved fatal. 



Hemorrhage Experiments. 



Although hemorrhage is one of the crudest factors for the 

 determination of physiological resistance, it has, nevertheless, the 

 advantage of being a real test, inasmuch as the production of new 

 blood is an exemplary reparative process. Hemorrhage, unlike 

 the injection of ricin, can also be gauged, to some degree at least, 

 to meet the individual resistance of the animal, as I have found in 

 these experiments. The procedure was uniform throughout this 

 part of the work. At the first hemorrhage from each animal, the 

 endeavor was made to take blood equivalent to 4 per cent, of the 

 body weight. After an interval of four days this procedure was 

 repeated ; and again eight days after the initial hemorrhage, 

 making three hemorrhages at successive intervals of four days. 

 All operations were conducted under ether narcosis. 



Six dogs were experimented on in this manner, three upon high, 

 three upon low, planes of protein nutrition, and four survived. Of 

 the two which died, one had been on a low plane of protein nurition 

 (0.4 gram of N per kilo) and one on a high nitrogen plane (1.4 gram 

 per kilo). Control animals on more extreme dietary conditions, 

 withstood the effects of greater hemorrhages. Therefore, it is 

 evident, I think, that these two deaths must be assigned to reasons 

 outside the realm of this research. In the case of the dog on the 

 high plane of protein nutrition, the cause is not far to seek ; the 

 dog was a collie, apparently pretty well bred, and it is a matter of 

 common knowledge that these dogs have very low resistance. 

 The dog that died on a low plane of protein nutrition was a fox 

 terrier mongrel. 



