408 STRONG AND CROWELL. 



and exercise may also be a factor in such instances in preserv- 

 ing the appetite. None of the subjects in our experiments did 

 any work or practically took any exercise. However, the diet 

 in which red rice formed the staple article was obviously the 

 most favorable one. The diet which consisted largely of extract 

 of rice polishings mixed with the white rice was the next most 

 favorable, while that one in which white rice formed the staple 

 article of diet was the least favorable of all. It is evident from 

 our experiments that beriberi may be produced by the prolonged 

 consumption of a diet in which white rice constitutes the staple 

 article of diet. Of the 17 individuals fed upon such a diet, 8 

 developed beriberi, and the stage of the disease was well ad- 

 vanced before the close of the experiment. All of these cases 

 had distinct loss of the knee jerk, in addition to other well- 

 marked symptoms of the disease. Symptoms of the disease 

 appeared in some cases in from sixty-one to seventy-five days 

 from the commencement of the diet, and the diagnosis was de- 

 finite and the knee jerks gone in one case as early as the sixty- 

 third day of the diet. In another case the knee jerks disap- 

 peared by the one hundred fifth day of diet. 



In Fraser and Stanton's experiments no case of beriberi oc- 

 curred in less than eighty-seven days, and the majority of the 

 cases occurred at a considerably later period, in from one hun- 

 dred twenty to one hundred sixty days. However, the indi- 

 viduals in their experiments were engaged in hard labor in the 

 open country. From their experiments and our own it would 

 appear that the incubation period of beriberi is not less than sixty 

 days. Undoubtedly, the incubation period varies with the char- 

 acter of the diet. None of the individuals in our experiments 

 developed symptoms suggesting scurvy. 



CONCLUSIONS. 



It is evident that among the individuals comprising our ex- 

 periments beriberi was produced only by means of the diet, and 

 that the disease has, therefore, a true dietetic causation. ■ It is 

 further evident from our experiments that beriberi develops 

 owing to the absence of some substance or substances in the diet 

 necessary for the normal physiological processes of the body. 

 Without the supply of such substances in the food, beriberi 

 results. Such a substance or such substances are evidently pres- 

 ent in red rice and in rice polishings and also in small amount 

 in the alcoholic extract of rice polishings, and when these arti- 

 cles are added to what would appear to be an otherwise phys- 



