Chapter XV 

 DIVERSE COMPONENTS 



§ 118. Total substance 



A variety of properties and constituents of organisms are now 

 to be considered with respect to maintenance. Total bulk of the 

 body is one. Are deficits of body substances compensated by in- 

 creased intakes, or by decreased eliminations, or by both? In 

 studying the maintenance of total body weight, all substances, in- 

 cluding water, are measured in the exchanges. 



04- 



UJ 





0.3- 



0.2- 



0.1- 



-12 



-10 



-8 



-6 -4 



Weiaht Load 



-2 



Fig. 153. Eate of weight exchange (% of Bo/hour) in relation to weight load (% of 

 Bo). Eabbit. Two deficits of body weight were previously produced by partial (A) or 

 complete (B) privation of food while water was available. Each point represents one 

 day during progressive recovery of 6 or 8 rabbits that were allowed a uniform food ad 

 libitum for 0.25 of the day. Rate of output was computed as rate of intake minus 

 rate of net gain in weight. Data of Maclagan ('37). 



Data for the rabbit record total intakes, and relate the intakes 

 to increments of weight. Elimination rates are computed from 

 intakes minus weight increments (fig. 153). Deficits are estab- 

 lished by complete or partial abstinence from food (either includ- 

 ing water or not), excesses are established by overfeeding or forced 

 intake. 



The relations shown are far from familiar to all who eat. Ee- 

 covery from deficit in the rabbit may occur not by augmentation of 



323 



