626 PHYSIOLOGY 



Those organs of the body which are most necessary for the maintenance 

 of life, the brain, the heart, the respiratory muscles, such as the diaphragm, 

 undergo very little loss of weight. Of the other tissues the fat, which is a 

 mere reserve to provide for such contingencies, is drawn upon first, and 

 during starvation 97 per cent, of the total fat of the body may be consumed. 

 The nitrogen needs of the body during starvation seem to be supplied chiefly 

 at the expense of the muscles and glands, which waste to a very marked 

 degree. The muscles being used simply as reserve material, it is easy to 

 understand the condition of lethargy and muscular inactivity which charac- 

 terises 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 from all the other cells of the body and so 

 maintain their weight at the expense of all other parts. A similar pre- 

 dominance 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 appearance, 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 osteo- 

 porosis. 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 development, 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 ascend. It takes no food. In the upper 

 reaches of the stream or river there is a growth of the genital glands, 

 ovaries, or testes. The whole material for the growth of these large organs 

 is derived from the atrophy of the skeletal muscles. In this case we 

 have the growth of an active tissue at the cost of an inactive one, the 

 activity, however, being determined, not by the direct call upon it from 

 the environment, but by what we may speak of as the ' physiological 

 habit ' of the animal. 



The animal organism, in the complete absence of food, deals with the 

 resources of its bodily tissues with the utmost possible economy. The total 

 metabolism therefore sinks rapidly during the first two days of starvation, 

 and then remains practically constant. There is indeed a slight continuous 

 diminution with -the fall in body weight, but if we reckon out the total 

 metabolism per kilo body weight, we find that till within a day or two before 

 death it is a constant quantity. This fact is shown in the following Table of 



