SOURCES OF ANIMAL HEAT AND MOTION. 85 
If it is admitted that the muscle-cells cannot generate heat 
without producing muscular motion (voluntary or involun¬ 
tary), then it is certain there must exist in the majority, it not 
in all animals, some other source of animal heat. The great 
bulk of the human frame consists of voluntary muscles, and 
these, in order to furnish the heat of the body (98°), would 
be kept in constant motion, for all force in the living organism 
must do its work the instant it is liberated. 
In cases of paralysis, the metamorphosis of the voluntary 
muscles is for a time suspended. Yet it is stated by 
M. Chossat that the temperature of paralysed limbs is but 
slightly lower than that of sound limbs. Professor Dunglison 
also states, that notwithstanding the usual depression of the 
thermometer in the neuroplegic side, it is not unfrequently 
found to be more elevated than in the sound side. I have 
“ neurotomized” more than fifty horses, but never observed 
any want of heat in the unnerved foot. 
I believe there now exists but little difference of opinion 
among physiologists respecting the uses of the fatty com¬ 
pounds which form so large a per-centage of the food of the 
herbivorous animals ; all agree they are converted (some¬ 
where) into carbonic acid and water, with the liberation 
of heat; but I fail to find, in the writings of any one, how 
or where this metamorphosis is performed; no tissue, no 
special cells, has yet been assigned for this important, ever - 
active function. 
No physiologist w T ill contend that heat is generated by the 
bones, the ligaments, or the tendons; the contraction of a 
muscle w e know must produce heat, but I am speaking of 
heat without muscular motion. The nerves are conductors of 
force, not of heat; heat cannot be derived from the brain, for 
in death from starvation the nervous centres scarcely exhibit 
any diminution in weight; it cannot be generated in the 
blood-vessels, for it is now generally held that the essential 
acting living organism is the untransformed cell. The 
only cells in blood (the corpuscles) are charged with oxygen 
—in fact, we may truly say, healthy blood is saturated wfith 
this element. 
I must here beg to conduct you as short a distance as 
possible over the uninviting field of minute anatomy. Exa¬ 
mined by the aid of the microscope, and magnified five 
hundred diameters, a perpendicular section of the human 
skin presents the beautiful structure seen in this drawing* 
The drawing illustrating this subject will be found at p. 247 of Car¬ 
penter’s ‘ Principles of Human Physiology,’ fifth American edition ; also 
in Kolliker’s ‘ Microscopical Anatomy,’ p 140 ; and in Griffith and 
Henfrey’s ‘ Micrographic Dictionary,’ p. 580. 
NXX1I. 
12 
