* 
the operations of digestion. The contact of food with the 
148 Organic Physics. 
from sleep, and if all wakening is not due to external influence | 
acting on the body, and through it affecting the mind. | 
The most simplified mode of activity in the higher animals is : 
that of the ciliated epithelial cells, which seem to respond to the | 
touch of mucus or other liquid substance. Their pe 
animal economy is, except in a few instances, very evident. E 
the principal mode of animal activity is that due to excitation 0 
nerve extremities, and the consequent effect upon the muse 
What is known as voluntary motion is obviously due to com 
of foreign matter with the external surface, its effects being P 
duced through the intermediate agency of the mind. It has: 
been fully perceived, however, that all involuntary motion is! 
toa like cause. This is, indeed, acknowledged to be the casei 
face of the digestive cavities is the influencing cause of all 
takes place. There are two distinct results of this contact. ° 
is the peristaltic motion of the cesophagus, stomach and intestines, 
by which the food is kept in motion, and is gradually pa 
downward. The other is the action on the glands that aid di 
tion. This is also largely muscular, being principally an 
on the walls of the blood vessels, which permits a free fl 
blood to the gland, and thus renders secretion more active. 
quantity of action in these two directions seems closely f 
to the vigor of food pressure, and all action ceases when the 
is empty of food, so that this principle of action keeps an 
harmony between the needs and the supply of motive ener 
digestion. 
A similar result of contact influence has been traced m 
teriorly, as in the action of the kidney ducts. Here every 
of the secreted liquid which exudes from the kidney cause 
staltic motions in the walls of the duct, which act to produce + 
ward movement of the liquid. | 
From these considerations it becomes probable that < 
„very important function is due to the same cause, althou 
thio mucin 
of the current i ses, the muscular 
vigorous, so that a close harmony I `I se and 
tablished, pens! between cause : 
tation of nerve extremities by blood pressure. As the p! | 
