PROTECTIVE AND EXCRETORY FUNCTIONS OF THE SKIN. 417 
dilate, 3. If a kitten with divided sciatic, and as a consequence 
dilated blood-vessels in the corresponding limb, be placed in a 
warm oven, the other feet will sweat, while the one the nerves 
going to which have been divided remains dry. 4. Perspira- 
tion will take place in a cat that has just died under the cir- 
cumstances mentioned in 1. From these experiments it is 
clear that nervous influences alone, in the absence of any vas- 
cular changes, or in the total deprivation of blood, suffice to 
induce the secretion of perspiration. 
If the central stump of the divided sciatic be stimulated, 
sweating of the other limbs follows, showing that perspiration 
may bea reflex act. It is found that stimulation of the periph- 
eral end of the divided cervical sympathetic leads to sweating 
on the corresponding side of the face. 
Human Physiology.—Certain nerves (e. g., the cervical sym- 
pathetic) have been stimulated with results similar to those 
obtained in other animals. We think these experiments and 
certain pathological phenomena, to be presently mentioned, of 
importance beyond their immediate application. They seem to 
show the influence of nerves over vital processes in the clearest 
way, and render it probable that this is the essential element in 
the highest vertebrates, and not the blood-supply, which, though 
important, is subsidiary. The path of the sweat-nerves is 
somewhat similar to that of the vaso-motor fibers, running 
mostly in the sympathetic in some part of their course. 
Whether there is a dominant center in the medulla and subor- 
dinate ones in the cord isa matter of uncertainty ; though, that 
the cerebrum can exercise a powerful influence over the sudor- 
ific glands is evident from the effect of emotions. 
Certain drugs seem to act on the centers through the blood; 
others on either the nerve terminals or the gland-cells them- 
selves. It is true that some of these will induce sweating after 
the nerves have been divided, though conclusions as to the nor- 
mal action of a part from such experiments must be drawn with 
the greatest caution. In our opinion they are rather suggest- 
ive than demonstrative in themselves, and the views we enter- 
tain of normal function should be formed from a consideration 
of all the evidence rather than that from a single experiment, 
however striking in itself. 
Sweating during dyspneea and from fear, when the cutane- 
ous surfaces are pale, as well as in the moribund, shows also 
the independent influence over the sudorific glands of the nerv- 
ous system. Heat induces sweating by acting both reflexly and 
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