NUTRITION AND GROWTH 



475 



(g) Diurnal variations. Botli wei<jht and height vary in the 

 course of 24 hours. The weight is lowest in the niornino- before 

 breakfast, and is highest after supper in the evening. This may 

 be aeeounted for by the fact that the weight of food eaten is greater 

 than the weight of excreta. On the other hand, stature decreases 

 during the day by from 1 to 3 cm. This trilling shortening is 

 attributed to compression of the intervertebral discs, curving of 

 the spine and depression of the arch of the foot. Measurements 

 for comparative purposes should, therefore, always be taken at 

 the same time of the day — e.g. before breakfast. 



{h) Nutrition. It is obvious that, if the animal does not get 

 an adequate supply of the material to be built into tissue, and 

 of the energy necessary for these processes, the work will be 

 done slowly and badly. In man at least, this only applies to 

 increase in girth and weight. Growth in stature seems to be 

 specific and is almost independent of the quality and quantity 

 of the food available. In the lower animals, while decrease in 

 growth is conspicuous in underfed animals, one may also detect 

 a clear falling off in the rate of increase of length (cf. Table 

 LXXXVI.). 



TABLE LXXXVI 



Comparative Weights and Lengths of Full Fed and 



Underfed Rats 



The underfed rats were given food of just sufficient energy content to 

 provide for their maintenance. 



It is well known that quite apart from its energy content, food 

 for growing animals must have certain of the amino acids in its 

 make up. These are the building stones or units of which the 

 complete organism is constructed. It has been shown that if 

 animals are deprived, say, of the amino acid ^ysin, their growth is 

 inhibited. On the addition of this amino acid to their diet, not 

 only is growth restarted but leeway is made up and a normal 

 growth is produced. 



Certain much studied but little known accessory factors are 

 absolutely essential constituents of the diet of the growing child. 



