WEIGHTS OF ORGANS IN UNDERFED YOUNG RATS 151 



This enables us to answer the question as to whether the organs 

 in young animals held at constant body-weight (and thus sub- 

 jected to a chronic inanition) behave in a manner similar to 

 adult rats during chronic inanition. In many cases, the group- 

 ing shows an agreement. The skeleton, eyeballs, spinal cord and 

 suprarenal glands have a strong growth tendency in young held 

 at constant body-weight, and also a strong tendency to main- 

 tain their original weight in adults subjected to chronic inani- 

 tion. The musculature, heart and kidneys approximately main- 

 tain their weight in young held constant, and maintain their 

 relative weight in adults during chronic inanition. In the major- 

 ity of cases, however, the behavior of organs in the young differs 

 materially from that in the adult. Thus the alimentary canal 

 has a marked growth in the young at constant weight, yet it 

 loses heavily during adult inanition. The converse is apparently 

 true of the thyroid gland. To a greater or less degree, this 

 inconsistency is seen in the case of most of the organs, as is 

 evident from table 25. 



This inconsistency is perhaps to be explained in the following 

 manner. In the adult during inanition the various organs lose 

 weight relatively in inverse ratio to the ability of their cells to 

 extract nutrition from the diminishing quantitj^ available in the 

 surrounding medium and to maintain equilibrium under these 

 adverse conditions. In the young animal held at constant body- 

 weight, the conditions differ in that the corresponding cells have 

 the capacity not only to 7naintain themselves, but to grow. The 

 growth capacity, as is well known, is different from and to some 

 extent independent of the maintenance capacity. The adult 

 has lost the capacity to grow, whereas the young animal has 

 both the powers of growth and maintenance. Hence their organs 

 behave differently during inanition. The alimentary canal, for 

 example, apparently has a strong growth tendency, but- a weak 

 power of maintenance. 



It is further evident, however, that even the growth capacities 

 of the various tissues and organs differ relatively from each other 

 under different planes of nutrition. Thus under normal con- 

 ditions of growth in the rat between three and ten weeks of age 



