DIVZESE COMPONENTS 



331 



tarv protein intake independent of total intake, and in most practi- 

 cal situations there is little opportunity for an animal to select 

 nitrogen intake independently of total energy intake. 



With all this in mind, it is scarcely worthwhile to believe that 

 present data yield more than a sketch (fig. 162) of a critically 

 derived equilibration diagram for nitrogen. 



The fact has been estabhshed that certain particular substances 

 are selected for ingestion by rats when these substances are de- 

 pleted. Such substances are water (Eichter, '36) and vitamin B 

 (Eichter et al., '37b, *3Sb). The increased "demand" for calcium 

 following parathyroidectomy (Eichter and Eckert. '37a) is mani- 



Total Nitrogen Load— qm^'Vij 



Fig. 162. Eate of total nitrogen exchange in relation to total nitrogen load. Xi- 

 trogen equilibration diagram. Dog. Only the qnantitr of whole diet was varied in each 

 individual, not the eonstitutents of the food, which differed in A, B from those in D, E. 

 A, four weeks of recoverv following partial privation of an adequately constituted diet 

 for nine weeks, individual of 13.94 kg. of Morgulis ( '23, p. 266) . B, previous balance 

 of same individuaL C, output in dailv periods of no food intake, individual of 5.S6 kg. 

 of Bubner ('02, p. 246). D, output in successive days of e:seessive food intake, same 

 individual. E, output in successive days of excessive food intake, dog ill of 4.1 kg. 

 of Bubner ('02, p. 113). 



fested by 3 to 6 fold increases in calcium lactate ingestion. Sodium 

 chloride is taken 6 times as rapidly as usual after adrenalectomy 

 (Eichter and Eckert, '3Sa) and during pregnancy (Barelare and 

 Eichter, '3S). Specific "appetites" of this sort have hardly been 

 measured in other species. Although in everyday life the animal 

 can do Uttle to unmix its foods, upon the specific appetites appears 

 to depend the maintenance of particular chemical constituents of 

 every individual. 



Excesses of food lead to faster recoveries of some constituents 



