1883. ] Growth and Development. 717 
GROWTH AND DEVELOPMENT. 
BY CHARLES MORRIS. 
Toe writer has endeavored to show, in a preceding paper, 
that all the activities of animal life are largely, if not entirely, 
dependent upon the action of external influences. A fuller con- 
sideration of this subject seems desirable. There is no question 
but that the voluntary motions are instigated in the lowest ani- 
mals directly by external stimulation. In the higher animals 
this instigation is partly direct and partly indirect, being largely 
that of mental influences, which arise from preceding individual 
or ante-natal impressions. Probably the involuntary motions 
have the same origin. We know that the digestive activities are 
set in motion by food pressure, and that the action of the kidney 
ducts is instigated by pressure, while it is not improbable that the 
actions of the heart and arteries result from a like influence. 
If this rule be as general as it seems, then the animal body has 
no innate power of motion. All its activity is accompanied and 
rendered possible by oxidation, which furnishes its force. If 
oxidation never takes place except through nerve stimulation, as 
there is reason to believe, and if all nerve stimulation arises pri- 
marily or secondarily through the influence of external force con- 
tact, then the animal body is simply a mechanism adapted to 
respond to the touch of outer force, and possessed of no inherent 
powers of activity. However sensitive it may become through 
nutrition, yet if utterly removed from external influence it must 
remain quiescent, since oxidation of its protoplasm could not 
take place. : 
The organization of the body of the higher animals is in close 
accordance with this idea. Every portion of it is brought under 
the influence of external force. There has been evolved a highly 
complex nervous system, with sensitive extremities on every por- 
tion of the surface tissue, and on all the active internal mem- 
branes, while motor fibers penetrate every region of the internal 
body, Thus almost every cell is connected with the surface by 
force-conveying fibers. And the surface extremities of the sen- 
Sory nerves are adapted to receive motor influences of almost 
‘very kind that exists in the external world. The skin is sensi- 
tive to the direct contact of moving matter and the vibratory con- 
1 
AMERICAN NATURALIST, February and March, 1883. 
