388 ON THE EXTERNA I, CAUSES OF DISEASE. 
The writer thus practically alludes to a fact which we have 
already endeavoured to impress on the minds of our readers:— 
that against the influence of noxious agents the living body is 
endowed with a power of resistance, which affords it complete 
security as long as its vital energies continue vigorous ; but when 
these decline, the very causes which before made no impression 
upon it, now prove fatal. Hence, the weaker the body, the 
more susceptible it is of the influence of physical agents, and 
the less it is capable of resisting the influence of those that are 
noxious. 
Air, moisture , and heat, are the principal agents which a 
living system has to contend with, and it is found capable of 
resisting them in proportion to the degree of vitality which it 
possesses. When the vital energies fail, putrefaction ensues, 
and it is soon resolved into the ultimate elements of which it 
was first formed. By this process, the stately oak and the 
bramble, the creeping insect and proud and imperious man, pass 
back to their original and primeval elements. Thus, to put an 
animal into “ good condition,” is to increase the preserving 
powers, which, as it were, preside over its economy, repel the 
attack of injury, and guard it from the dangers with which it 
is incessantly surrounded. This leads us to another part of our 
subject, viz. food. 
We have now considered in succession a number of the pro¬ 
perties of the atmosphere; and its contemplation as a machine 
(if it may be so called) is well suited to impress upon our minds 
the strongest conviction of the most refined, far-seeing, and far- 
ruling contrivance. It seems impossible to suppose that its va¬ 
rious properties were bestowed other than by a beneficent and 
intelligent Being—able and willing to diffuse organization, life, 
health, and enjoyment, through all parts of the world. 
Quid sit pulchrum, quid lurpe, quid utile, quid non.—lion. 
Hippopathology :— A systematic Treatise on the Disorders 
and Lamenesses of the Horse. By William Percivall, 
M.R.C.S ., Veterinary Surgeon in the First Life Guards, 
Co-editor of “The Veterinarian f and Author oj “The Anatomy 
of the Horse.” Longman and Co. 10s. 6 g?. 
It is one of the taxes which we have to pay for our supposed 
editorial privileges and advantages, that we are, in a manner, 
forbidden to refer to or quote from our own works—that would 
