566 
ON ANIMAL UK AT. 
in other parts of the body may materially assist in its elimination. 
By receiving this explanation we can readily account for the 
phenomenon of evolution of heat resulting from increased circula- 
tion, which was inexplicable on the respiratory theory alone. 
It explains why the warmth of old persons (13) diminishes. 
Their tissues gradually assume a less elastic character. The 
arteries themselves often become ossified in distant parts of the 
body, giving rise to gangrena senilis, from a loss of the elastic 
power and consequent diminution of temperature. 
This view also accords with the facts noticed with respect to 
the diurnal variation of animal temperature (14), and also with 
its being lower during sleep ; both being regulated by the inten- 
sity of the circulation. 
That digestion (15), by rousing the powers of the body, should 
slightly increase its temperature, admits of explanation on the 
same grounds. The mechanical distention of the stomach, to- 
gether with the contraction of its muscular fibres, may have a 
tendency to increase the effect produced by a vigorous circula- 
tion. 
If it be a fact that ceruleans have a low degree of vital heat 
(19), it would certainly tend to justify the arguments of those who 
assume respiration to be a source of animal caloric, and it might 
go far to prove to what extent its influence prevailed. That dis- 
ease, in which the circulation of the blood is obstructed and un- 
natural should produce a lower temperature, is easily conceivable. 
If the temperature of paralysed parts (19) is decreased, the 
wasting in bulk of a limb so affected shews evidently that the 
circulation is obstructed. 
Obstructed circulation may also be referred to as the cause of 
the diminution of heat in various diseases, and in syncope (19), 
when the action of the heart is temporarily suspended. 
The heat eliminated by sudden determination of blood pro- 
duced by the excitation of the mental organism (20), may be 
viewed as resulting from a peculiar excitement, directing an in- 
creased flow of blood to the superficial arteries. 
That muscular exertion should be productive of warmth (21) 
may, as has been before hinted, arise from the operation of two 
causes, — increased circulation through the muscular tissue, and 
throughout the body, when muscular action is considerable, and 
on a physical generation of caloric during muscular contractility. 
In diseases where the action of the circulatory organs is unduly 
increased (20), and the countervailing influence of perspiration 
stopped, it is not surprising that the free caloric should be con- 
siderably above par. The same remark applies to the more cir- 
cumscribed abnormal actions, as the tumour, wherein MM. 
