376 
RESPIRATION. 
edly depending upon the extent to which the unequalization of 
nervous influence has advanced. Hypertrophy or atrophy or both 
may result to the laryngeal muscles from an irregular distribu- 
tion of the nervous stimulus. 
It is common to say, that the wasting of the muscles arises 
from loss of action in them, consequent on some unfavourable 
position of the head and neck being maintained for some consi- 
derable period ; and that the hypertrophic state of the oppo- 
site muscles proceeds from increased action in them, owing to 
the suspended condition of those that are atrophied. For my 
own part, I cannot very clearly observe any position of the head, 
however long it may be continued, that could produce such 
effect upon the muscles of the larynx, so long as respiration is 
carried on with natural vigour. Compression of the neck by the 
cribbing-strap would, on a first view, appear more feasible: still, 
this strap is never applied so tight as to interfere with the horse’s 
respiration ; and, what is more opposed to such an opinion, is the 
fact of animals so treated not becoming roarers in consequence. 
Some few doubtful cases may be brought forward in support of 
it ; but that numbers of horses have worn the neck-strap for a 
very long time and not become roarers is a well-established fact. 
Every part of the frame is preserved in its healthy proportion 
by the influence of its vital endowment, which keeps up a con- 
tinued vital attraction of molecules from the blood, and these in 
quantity sufficient to replace such of those particles as have lost 
their vital affinity, and are carried away by a process of absorp- 
tion. The process of formation of parts from the blood, and the 
removal of particles, by absorption, which are no longer useful to 
the purposes of structure, is liable to be disturbed in its progress. 
When the vital influence of a muscle or other structure is nro- 
ceeding with activity, the attraction of the nutrient particles 
from the blood, similar to those of the tissue they are to consti- 
tute, is vigorous and extensive, separating a greater number of 
the molecules, depositing them in closer affinity, and the sub- 
stance of the part becoming augmented. Should, however, the 
extent of the vital endowment be diminished and weakened, then 
the vital attraction is comparatively languid, the affinity existing 
between the molecules is rendered weak, and their removal by 
absorption proceeds quicker than in health, and more rapid than 
they are deposited — thus the muscle or part wastes, or becomes 
deficient in its constituent particles, or atrophied. 
The healthy function of a muscle, together with its proper pro- 
portions, is 'dependent upon an equilibrium being maintained be- 
tween the influence of attraction and vital affinity ; and upon the 
due supply of nervous power and the vigorous state of the circula- 
