330 PHYSIOLOGICAL CHEMISTRY 



own proteids are attacked, i. e., it consumes itself. This is probably 

 the most important reason why a definite minimum amount of pro- 

 teids is essential in a small total amount of nutriment. That further 

 differences exist among the individual organs themselves is still to 

 be proven, but at present it appears quite probable. 



A third ground has been disclosed during the past few years by 

 the work of the great Russian investigator, Pawlow. We know from 

 this that the nervous connection of the digestive system with the sense 

 organs of the head determines the enjoyment of the food, and hence 

 regulates the choice of that. We know further from Pawlow, Wein- 

 land, and Starling that this connection is not fixed once for all, but 

 varies according to the needs of the time. When any such relation 

 is observed we must always conclude that it is adapted to an end, for 

 otherwise it would have disappeared within a short time. Pure pro- 

 teids are tasteless and odorless, and also fail to act upon the sensi- 

 tive nerves of the stomach and intestine; in all natural foods, on the 

 other hand, the proteids are always associated with the pleasant- 

 tasting constituents of nutriment, and those which stimulate diges- 

 tion. For us, just as for the carnivorous animals investigated by Paw- 

 low, the substances richest in proteids are always the most pleasant to 

 the taste, and those which arouse the appetite the most. The foods 

 which are poorer in proteids, as rice and potatoes, stimulate the diges- 

 tion less and consequently are more difficultly digestible, A food-stuff 

 free from proteids has already been shown in animal experiments to 

 be impossible as a diet, and even in experiments with substances which 

 are poor in proteids Siven and Rohl encountered insurmountable dif- 

 ficulties owing to the tastelessness of the material. 



Even though we do not as yet know all the reasons, it is at any rate 

 obvious that, for long periods of time and for normal nutrition, Voit 

 has discovered the correct condition, viz., that an amount of proteids 

 equal to 100 gr. per day is essential, or at any rate can be designated 

 as desirable. 



Since in consequence of the special internal organization of the 

 human body, and because it is the minimum amount used by all men, 

 this amount of proteids is independent of the form of nourishment 

 absorbed, and independent of the habits of life. Even as early as 

 1860 and 1866 Voit showed that the protein consumption of those 

 doing hard work is not greater than of those who do none; and this 

 result has been confirmed many times. The American physiologist, 

 Atwater, has made an especial study of this question, using his 

 respiration calorimeter. As the average of numerous experiments, 

 carried out with the greatest exactness, he found that the subject 

 of experiment, whether resting or working, decomposed the same 

 amount of proteids, even when the production of calories by the 

 work rose to double or more. Indeed, the decomposition of proteids 



