700 PHYSIOLOGY 



characterises the state of inanition. During starvation all tissues 

 of the body undergo a process of autolysis or disintegration, giving 

 up the products of this process to the common circulating fluid. 

 The nutritional demands of a tissue are determined by its activity. 

 Hence the active tissues of the body take up the material set free 



Loss IN WEIGHT OF DIFFERENT ORGANS DURING STARVATION 



from all the other cells of the body and so maintain their weight 

 at the expense of all other parts. A similar predominance of the 

 nutrition of active over inactive tissues is to be observed in cases of 

 partial starvation, i.e. where the deprivation of food only applies 

 to a single food constituent. Thus Voit, in a series of experiments, 

 fed pigeons on a food which, while normal in all other respects, 

 contained a deficiency of calcium salts. On killing the birds after 

 a certain length of time, it was found that while the bones used in 

 the necessary movements of the animals presented a normal appear- 

 ance, the others, such as the sternum and skull, showed a marked 

 deficiency of lime salts and had undergone a process of rarefaction 

 giving rise to the condition known by pathologists as osteoporosis. 

 Many other instances of the sacrifice of a temporarily useless tissue 

 on behalf of tissue of high physiological value are known. Thus 

 the salmon and its congeners, which live part of the year in the sea, 

 lay their eggs and undergo their early development in the fresh water 

 of the upper reaches of rapid streams. An adult salmon leaves the sea 

 in the early summer months in a magnificent state of muscular develop- 

 ment, fit to perform the prodigious feats of swimming which are 

 required in order to get it over the rapids of the river which it has to 



