STUDIES IN THE REGENERATION OF BLOOD 



out hemorrhage was starved at the same time; its blood was found to 

 vary no more in red cell count and hemoglobin percentage from day to 

 day than that of a normal animal eating as much as it desired. Normal 

 rats do not maintain wholly constant values for either hemoglobin 

 percentage or number of red cells. This slower rate of regeneration 

 during inanition is in agreement with the results of Hooper and 

 Whipple (11) on fasting dogs after simple anemia (table 5). 



Protein only. Since casein is the protein used in our standard synthetic 

 diet and has been shown to be an adequate protein (2), this was fed 

 as a sole source of nourishment to another group after hemorrhage 

 until blood regeneration was accomplished. Only 2 grams per day per 

 animal were used after it was found that the rats refused to eat more 

 than this amount in that period. This limited protein diet was used 

 to see whether in accord with the experience gained with the protein- 



TABLE 5 



Blood regeneration in adult rats after a single hemorrhage; during this period they 



received no food 



rich diet of dogs (11) the rate of regeneration was more rapid than on 

 other diets of one food factor only. 



The tune of blood regeneration in this set of experiments was from 

 9 to 12 days, more rapid than in starvation but not so rapid as on some 

 other equally limited diets (table 6). It must be borne in mind how- 

 ever that no food accessories (vitamins A and B) were present and 

 hence the animals ate less than they otherwise would. The energy 

 intake was obviously inadequate so that underfeeding complicated 

 the problem. In all these feeding periods where the diets were limited 

 in amount or kind, or both, the rats were more coprophagous than 

 normal, no doubt in an effort to satisfy their desire for a feeling of 

 fullness. 



Fat only. In feeding the fat portion of the basal diet, butter washed 

 free of salt was used in an amount corresponding to the daily weight 

 of protein fed. The rats did not eat the butter readily and never ap- 



