12 



BODY WEIGHTS. 



The weights of the body were ascertained by means of a platform 

 scale with agate bearings, and of a delicacy sufficient to register easily 

 differences of weight of 10 grams when carrying a man of average 

 weight. The subjects were weighed naked, as it is not safe to assume 

 that the weight of clothing remains constant, for even if the same kind 

 or character of clothing be worn, the variation in weight is very great 

 because of changes in the hygroscopic condition of the atmosphere. 

 Thus a given amount of clothing would show very different weights on 

 a dry and on a wet day. 



In the general discussion of the influence of weights it is always i 

 advisable to take the average weight for a period of days rather than 

 the separate weight for any one day. In the interpretation of the value 

 of the body weight it should not be forgotten that a loss in weight must 

 not be interpreted to mean always defective nutrition, nor a gain in 

 weight be attributed always to conditions favorable to health. The 

 accumulation of an excessive amount of fat is not an evidence of excel- 

 lent digestion or normal increase. It may be due to a perversion, to 

 some extent, of the processes of assimilation. On the other hand a. 

 loss of weight is not always to be interpreted as indicating an unfavoil 

 able condition of nutrition, because in persons who indulge in overl 

 feeding, or who have accumulated excessive fat for other reasons, a 

 diminution of weight may be distinctly favorable to better digestion anl 

 health. Nevertheless, in a state of normal equilibrium when the food 

 supply remains constant, any marked variations in weight can not bf 

 regarded as wholly normal. 



DIFFICULTIES CONNECTED WITH THE WORK. 

 COLLECTION OF EXCRETA. 



Aside from the usual difficulties connected with analytical practice^ 

 which must always be taken into consideration, there are some special 

 points in connection with a work of this kind which must be mentioned. 

 These difficulties are connected chiefly with the collection and analysis 

 of the excreta. The principal object in the analysis of the excreta, as 

 is evident, is to establish the relation between certain ingested elements 

 and those which appear in the excreta. Certain forms of food are more 

 or less completely changed in passing through the body, and are oxi- 

 dized and manifested as heat and energy. The fats and carbohydrates 

 are types of food of this kind. Certain other elements in foods, while 

 they undergo marked changes of combination during digestion, assimi- 

 lation, and excretion, appear in the excreta in practically the same 

 quantity in which they are found in the food. Among these substances 

 may be particularly mentioned nitrogen, sulphur, and phosphorus. 



In a state of equilibrium, where the body is exercising all of its func- 

 tions in a normal manner, and where there is neither increase nor 



