349 DR ALISON’S OBSERVATIONS ON 
tions of matter which are brought to particular points in previously existing or- 
ganized structures ; they are vigorous for a time, and are then lost. In all the 
compounds constituting the animal textures, these affinities become gradually 
enfeebled, whereby the elements constituting these textures become liable to ab- 
sorption into the blood, to changes in their arrangements, chiefly effected by the 
oxygen of the air, to combinations with the redundant matters above noticed, and 
to the formation of other compounds in the blood, which are either the same as, 
or rapidly tend to, the combinations with oxygen to which animal matter is liable 
in the dead state; which are, therefore, properly speaking, due to simply che- 
mical affinities, and therefore crystallizable, like other inorganic compounds, and 
are noxious to the animal economy. This is another source of the excretions, 
for the separation of which appropriate organs are furnished, capable by their 
vital power of absorbing and abstracting them from the blood. 
9. That the simply chemical power thus exerted by the oxygen, taken in by 
respiration, over the redundant (especially non-azotised) matter in the blood, 
and the efete matter of the textures, is the source of Animal Heat. 
10. That there is thus effected during the life of animals, but in consequence 
of the failure of their vital affinities, and restoration of the simply chemical rela- 
tions of their component elements, a change equivalent to the slow combustion 
of the organized matter, which had been first prepared by the vital affinities of 
vegetables; and that the carbon, hydrogen, and other elements employed in the 
formation of that matter, are thus continually resuming that condition, from 
which the power of vegetable life is continually abstracting them again, to com- 
municate to them a set of properties at variance with those which they perma- 
nently possess; and apply them to a succession of organized beings which can 
only terminate, as at no very distant period of time it must have originated, by 
an arbitrary act of Divine power. 
The gradual change both in vegetable and animal structures which results 
from age,—the increase of the proportion of earthy and saline matter, and dimi- 
nution of the proportion of strictly organic matter,—must be regarded as indi- 
cating a peculiarity of the vital affinities equally an ultimate fact as their limited 
duration in every portion of a living body. And the modification to which these 
affinities, as well as all other strictly vital powers, are liable in animals, from 
certain actions of the nervous system, must likewise be regarded as an ultimate 
fact, quite distinct from any principles that have been ascertained in regard to the 
nature of the vital affinities themselves. 
On reviewing the statements and reasonings which I have laid before the 
Society on the subject of Vital Affinity, although | may have committed errors in 
the details, I cannot accuse myself of having occupied their time, either with a 
vague and useless speculation, or with a verbal dispute. 
That there is something in the history of all living bodies which is peculiar to 
