I908.1 UPON HEALTH AND METABOLISM. 307 



The study of the food ingested and of the excreta secured estab- 

 lished a chemical control whereby it would be easy to determine 

 any variation in the quantity of food consumed should any of the 

 young men attempt to evade the conditions of their pledge. Hav- 

 ing thus established the normal conditions of the body and ascer- 

 tained the normal metabolic processes, there was introduced into the 

 same ration varying quantities of the preservative which was to be 

 studied. It was thus evident that any change taking place in 

 health or metabolism could be due only to the one factor which 

 was varied in the method of life, namely the injection of the 

 chemical preservative. This period, during which a drug was used, 

 was known as the " preservative period," and lasted, according to 

 circumstances, from twenty to sixty days, depending upon the char- 

 acter and magnitude of the effects produced. As soon as any de- 

 cided disturbance of health was produced, clearly traceable to the 

 administration of the preservative, its future use w'as discontinued 

 since it was not the purpose to seriousl}^ or permanently affect the 

 health of the subject, but only to secure positive diagnostic data. 

 Then followed an " after period," during which the chemical, or 

 drug, was withdrawn from the food and the normal ration con- 

 tinued as in the fore period, the object being to correct, if pos- 

 sible, any disturbances of metabolism which had been produced 

 and restore the subject again to normal conditions of health and 

 digestion and also to study the after effects of the preservative 

 should such persist. This period of observation w^as called the 

 " after period." Thus each series of experimental investigations 

 were divided into these three periods. 



During the progress of the experiment the following substances 

 were added to the foods for the purposes mentioned above : Boric 

 acid, borates, salicylic acid, salicylates, benzoic acid, benzoates, sul- 

 phurous acid, sulphites, formaldehyde, sulphate of copper and potas- 

 sium nitrate. There is given in the accompanying table a condensed 

 statement of the eft'ects which were produced in these various cases. 

 It is not the purpose of this paper to go into the experimental detail 

 of this matter. The amount of chemical analysis incident to this 

 study was enormous. A great many chemists gave their entire time 

 during the whole period of observation to these analytical problems, 



