I893-] 63 [Hyatt. 
animal from a very early age. He was so much impressed by 
these facts that he characterized the whole life of tlie individual 
as a process of senescence or growing old. 
Although this term seems to be defective, since the word senile 
has an accepted popidar and scientific meaning and an appropriate 
application in morphology to a distinct period of ontogeny, Dr. 
Minot's facts are no less significant and show that we cannot make 
any distinction between the progressive and retrogressive or senile 
stages of the develoi)ment of the individual in terms of growth 
force. Growth isessentiallj^ a constantly decreasing force even in 
the progressive stages of development. In other words increase 
of bulk, and development as manifested by the addition of charac- 
teristics, are more antagonistic than has been supposed. The 
increase in the bulk of the body by fission of cells and, even as 
stated by Minot, the increase of cytoplasm around t,he nucleus of 
the cell itself, must be regarded as a load upon growth force. 
This force according to Minot can be measured by the proportion- 
ate amount of nuclear substance, which is largest in the cells at a 
very early pei-iod of development and then constantly decrenses 
with age in pro])ortion to the elaborated cytoplasm. 
Naturalists have, as a rule, understood the differences between the 
organic molecular increase that takes place within cells, which is 
the simplest form of growth, and that which follows this and builds 
up tiiC tissues of the body by the division of cells. Both of these 
processes although distinct from each other result in additions to 
the bulk of the organism and come properly under the head of 
growth. But while both are thus constructive so far as the body 
is concerned, only one can be considered constructive or anabolic, 
while the other is essentially destructive or catabolic, so far as the 
cell itself is concerned. 
The cell grows by internal additions and this process builds it up, 
but when the differentiations which lead to subdivision begin in 
the nucleus and cytoplasm, tiiis is as purely the develojjment of 
characteristics by the breaking down and specialization of the parts 
of the nucleus as is the subsequent fission or breaking down of the 
cell itself to form daughter cells. Nevertheless, so far as the 
increase of the bodies of Metazoa is concerned, the latter is 
substantially a constructive process. The process of growth is 
therefoi-e first the anabolic increase in size of the cell itself l»y the 
assimilation of foreign materials, second the breaking uj) or 
