54 PRESERVATION OF FOOD BY REFRIGERATION ; 
which produces molecular motion also produces heat, and 
that, so far as the substance heated is concerned, the result 
is identical by whatever means the motion is produced. 
Consequently, ‘animal heat” does not differ zz kind from 
the heat produced by any other form of energy, being heat 
developed in the body of a living animal as the result of chemi- 
cal separation, etc. To those unacquainted with the opera- 
tions of the laws governing the changes of state which occur 
when chemical decomposition takes place, it would seem to be 
of a different order to the heat generated by, say, a fire, or a 
steam pipe. Such is, however, not the case, as, if ‘‘ animal 
heat’ were other than dynamical, its action would not be 
manifested in the same manner, and we should require 
other means and apparatus to detect it. As, however, all 
its indications and manifestations are perfectly in 
accordance with, and capable of being referred to, the 
dynamical theory, and produce exactly the same results 
upon the animal tissues as those produced by the ordinary 
forms of energy, we are justified in stating that there is no 
difference zz kind between “animal heat” and any other 
heat. Nor is it conceivable that there could be any, for if 
we trace the operations of the vital processes, we find that 
the “animal heat” is produced by three distinct forms of 
energy, all of which exist and operate in exactly the same 
manner outside of an organised body as init. These forces, 
or forms of energy, are the energy of chemical separation, 
the energy of absorbed heat or friction, and the energy of 
electrical separation. Although the vital power which calls 
these energies into play in a living body is undiscoverable 
and totally beyond our present comprehension, still we can 
produce exactly the same results with inorganic compounds, 
generate heat by friction or electricity, and measure with 
great accuracy the amount of heat (or motion) produced. 
Box, in his treatise on heat, makes the following remarks 
on this subject :— 
‘‘ In the act of respiration, oxygen derived from the atmospheric 
air combines with carbon and hydrogen given out from the lungs, 
the carbon being transformed into carbonic acid and the hydrogen 
into water or vapour. It is shown that combustion, by which heat 
is obtained in our furnaces, is effected by similar combinations, so 
that respiration is a veritable act of combustion at a low tempera- 
