180 Dissertation on Animal Heat. 
The fact of this equi-balanced attraction may be easily com- 
prehended in spite of the intervention of a substance, such as car- 
bon, which exhibits in itselfso powerful an attraction for oxygen. 
It is sufficient to reflect that this substance is here destitute of 
the degree of heat necessary for acting with efficacy on the base 
of oxygen gas, and that the union of two combustibles, especially 
when they are both disposed to assume the gaseous state, in- 
creases considerably their affinity with that base. I believe even 
that in this case the carbon requires to be united to a small por- 
tion of hydrogen, in order to be assisted in its attraction for the 
oxygen, and that the azoto-hydrogenous compound requires, on 
the same principle, a little carbon in order to retain its identity. 
It is easy to perceive what ought to be the effect of the circu- 
lation of a compound thus constituted, and in which the oxygen 
remains charged with nearly the whole of its immense provision 
of caloric. It is unnecessary to state, that the affinity of the as- 
similating power for one or other, or for the whole of these prin- 
ciples, must very soon destroy that combination, and that the oxy- 
gen disengaged from those channels which prevented it from en- 
tering intoa more solid combination, must either contract a similar 
union, partly with the hydrogen which only decomposes it par- 
tially, and partly with the carbon which extracts from it the greatest 
possible quantity of caloric, or that it must be itself assimilated ; 
and that in either of these cases it must lose by little and little 
that caloric which aslighter affinity had permitted it to preserve, 
This decomposition occurs principally in the extremities of the 
arterial vessels, and is perhaps continued, though with less energy, 
and by ways as yet little known, after the arteries are reunited 
with the veins, and until the return of the blood to the heart. 
We may conclude then, that in all those functions which de- 
pend on decompositions and compositions by chemical affinity, 
(and there are few which are not in this situation,) the undecom- 
posed oxygen continues to consume, more or less completely, one 
or other of the combustible substances which form the base of 
animal composition. It must be necessary accordingly that there 
should be a disengagement of caloric every where, or a similar ac- 
tion takes place, either by the oxygen of the oxidized blood, or 
by that which is separated from the water when that action passes 
beyond the sphere of circulation. 
The action of vegetable life differs from that of animal life in 
this respect ; that in the first the assimilation is effected by the 
condensation of the carbon and hydrogen with a disengagement 
of oxygen; and that in the latter every thing is effected by the 
intervention, and by a more solid condensation, of this principle. 
XXVIII. On 
