46 Scientific Reviews. 
ing which he founds, or the principles which he deduces from im- 
portant results, are occasionally far from being either legitimate or 
correct,” (Introd. p. xiii.) But the application of observations 
conducted by the author, in elucidation of the cause of the uniform 
temperature of the arterial blood over the surface of the body, is 
highly valuable, as tending to remove the great objection to the 
chemical theory of Black. When this celebrated chemist advanced 
the opinion, that a process analogous to combustion takes place in 
the lungs, it was a natural objection that they would, in that case, 
become much warmer than any other part of the body, which is 
contrary to the fact. Crawford for a time removed this difficulty, 
by the publication of experiments to show that arterial blocd has a 
ae capacity for heat than venous bleed. More recently, Dr. 
fohn Davy has produced experiments which do not accord with the 
conclusions of Crawford. It was then that physiologists plunged 
into their last resource, where mystery shrouds the truth, and attri- 
buted the production of animal heat to “the influence of the 
nerves.” Dr. Holland now proposes that it is not the quantity of 
-axygen which is inspired, but the frequency of inspirations, by 
which a greater or less surface of blood is exposed to the air during 
a given time, that forms the ratio according to which animal heat 
is generated, and the smaller the quantity of blocd in the lungs, 
the more complete will be the chemical change, “ because the air. 
will have a less portion to oxygenate.” He appropriates indepen- 
dent functions to the acts ef inspiration and expiration, the former 
accelerating, the latter impeding the circulation of blood throughs 
out the system, and thus varying the proportions within the chest 
at different times. As an enlargement of these principles, the au- 
thor advances (inter alia) the following laws as universal : 
“1. That, in every case, in which inspirations preponderate, either in number 
er completeness, the pulse will be small, weak, and for the most part frequent ; 
the surface and extremities of the body pale or collapsed, and the temperature of 
the system less than in the regular action of the two states of respiration. 
“ 2. In every instance in which expirations exceed inspirations, either in num- 
ber or completeness, the pulse will be strong and frequent, the surface and extre- 
mities of the body florid and full, and the temperature of the system higher than 
natural. 
“ 3. The influence of cold upon the surface of the body will diminish the ge- 
neration of animal heat, according to the degree of congestion produced in the me 
ternal viscera. 
_ “4, The influence of heat applied to the same parts, will increase the tempe- 
rature of the body, according to the relief which it gives to the internal organs, 
by diffusing more generally and equably the circulation of blood. 
2 = & & s % % & 
“7. Every exertion characterised by muscular and expiratory action will in- 
crease the temperature of the body, and tend to equalise the circulation. 
“ 8. Every exertion characterised by muscular and inspiratory action will di- 
miinish the temperature of the body, and tend to destroy the regular distribution 
of the blood. 
“9. The effects of respiration, on the animal economy, can be estimated only 
by ascertaining the character, frequency, and force of the acts of which it is com- 
posed.” —P. 20. 
