362 THE BIOLOGY OF THE SEASONS 



else a typical wild animal does with its income besides 

 growing in size and weight, we find it difficult to believe 

 in the " gradual loss of vitality " which seems to Professor 

 Minot to be a general phenomenon of life. 



Minot has sought to establish a second corollary of his 

 law, that as the body grows older there is an increas- 

 ing disproportion between the cell-substance (cytoplasm) 

 and the nucleus (nucleoplasm) . He believes that the 

 cytoplasm increases out of proportion to the nucleoplasm, 

 and thus interferes with the power of growth. It is inter- 

 esting to find that Minot's views as to the importance of 

 the relation between nucleus and cell-substance, which 

 were first stated in 1890, have found of recent years con- 

 siderable confirmation. Professor Richard Hertwig of 

 Munich has brought forward a large number of very in- 

 teresting facts showing the importance of the relation 

 between nucleus and cytoplasm, and has given an elaborate 

 discussion of the whole subject. 



Somewhat analogous to Minot's view is that of Kasso- 

 witz, who points out that as life goes on there is more and 

 more accumulation of what one may call half-used sub- 

 stances, such as fat, the body becoming, as it were, smothered 

 in the results of incomplete combustion. 



Demange, the author of a French treatise on old age, 

 seems to interpret all the phenomena in terms of the 

 degenerative changes in the walls of the arteries. These 

 show hardening or sclerosis, the nutrition of surrounding 

 cells is thereby lessened, and atrophy sets in. As is often 

 said, " A man is just as old as his arteries." There can be no 

 doubt as to the importance of this view, but we wish to 

 know why the arterial wall should become sclerotic. More- 

 over, the theory is far too human in its reference ; many old 

 animals show no trace of arterial sclerosis. 



According to Metchnikoff, the symptoms of old age 



