Effect of Variable Intake on Body Composition 133 



which may be given up by an organ or tissue under uniform 

 conditions without interfering with organ or body function- 

 ing." This definition indicates primary physiological signific- 

 ance, not anatomical. In this view the primary requirement 

 for furthering understanding would be methods for character- 

 izing and distinguishing physiological depletion. The response 

 to repletion has been used to assess the degree of depletion in 

 such a physiological sense. The work of Madden and Whipple 

 (1940) and Cannon (1954) illustrates the fruitfulness of the 

 method for studying the metabolism of protein under con- 

 ditions of deficit. Cooke and co-workers (1952) and Schwartz, 

 Cohen and Wallace (1955) have applied the technique to 

 experimental potassium deficiency and Hansen (1956) to the 

 potassium deficit in kwashiorkor. The ability to survive in 

 stressful situations provides a further avenue of approach. 

 Baur and Filer (1957), employing the weanling pig growing 

 on diets similar to those used in the present experiments, 

 have shown differing abilities of animals growing on different 

 diets to resist water and caloric deprivation. Their data 

 indicate that animals maintained on low protein intakes 

 survive caloric deprivation to a greater degree than do those 

 maintained on high protein intakes. Conversely, the high- 

 protein-fed animals withstand water deprivation to a greater 

 degree than do their low-protein-fed companions. Sherman 

 (1946) has correlated calcium intake with life span and 

 reproductive life. A newly opened approach to the problem 

 of characterizing and assessing deficits in a physiological 

 sense is that of distinguishing structural versus enzyme protein 

 in tissues. Potter and Klug (1947) have shown that liver 

 octonoate and succinate oxidases are depressed in animals fed 

 varying levels of protein. Miller (1948) Lightbody and Klein- 

 man (1939) and Williams and Elvehjem (1949) have extended 

 these observations to a number of other tissue enzymes. 



Summary and Conclusions 



The composition of growth of the albino rat on high protein- 

 high electrolyte, on high protein-low electrolyte, on low 



