STATE OF NUTRITION. 201 



capable of any material alteration? Are there variations in it? If so, 

 how wide, and can conditions be imposed upon the body so as to lower 

 the basal metabolism? It is very clear to students of metabolism at 

 the present time that one of the greatest factors in metabolism is 

 the stimulus to cellular activity which is continually acting upon 

 the body-cells. Can the stimulus be lowered? It has been shown by 

 giving a carbohydrate-free diet, thereby developing an acidosis, that 

 the acids do stimulate the cells to greater activity, with a resulting 

 greater metabolism. Is it possible to reverse this condition? The 

 normal existing stimulus consists of acids, chiefly amino, flowing 

 through the blood-stream. It is conceivable that by reducing these 

 amino acids, providing the theory of acid stimulus is true, the basal 

 metabolism may be markedly lowered. 



In the subsequent discussion special emphasis will be laid upon 

 those features of the research that contribute to the question of the 

 factors relating to cellular stimulus, most marked among them being 

 the withdrawal from the body of rather large amounts of nitrogen, as 

 indicated by the pronounced negative nitrogen balances found with all 

 of the subjects. 



It is indeed surprising that after 15 years' search for a nutritional 

 level with man markedly different from that of the normal individual, 

 such a level should not have been found in all the researches conducted 

 by this and other laboratories. With animals other than man, changes 

 in the nutritional level are by no means unconmion in nature. One 

 has but to think of the long period of hibernation of such mammals as 

 bears, during which the metaboUsm is sustained, although at a very 

 much lower level than normal. With marmots it has been shown that 

 the body temperature is also much lower than normal. In other words, 

 during hibernation we have animals approaching the cold-blooded 

 stage. Prior to hibernation there is a large accumulation of fat ; during 

 hibernation there are, of course, drafts upon body-material to sustain 

 life, even at the lower metaboHc level. It is furthermore worthy of 

 note that with bears, at least, the birth of young occurs during 

 hibernation.^ It would seem to be a provision of nature that these 

 animals born during hibernation have an extraordinarily small birth- 

 weight. Instances are not uncommon of bears weighing over 500 kg. 

 having young with a birth-weight of 500 grams. Furthermore, after 

 birth there is a relatively long period of suckling, in which the bear cub 

 subsists wholly upon its mother's milk, this period occurring entirely 

 during hibernation. This small birth-weight in proportion to adult 

 weight — a proportion that we believe exists nowhere else among mam- 

 mals—is unquestionably a minimizing of drafts upon body-material 

 during hibernation. 



* Personal comndunication from Dr. C. Hart Merriam, Washington, D. C. 



