308 
RESPIRATION. 
faces of the peritoneum generally, as in the omentum, mesentery, 
or intestines— is an inactive weight upon the expiratory muscles, 
and to be moved by their power of contractility. The blood in 
circulation may impede respiration by volume or quality; the 
composition of the blood is not a subject entering into the me- 
chanism of respiration : suffice it to say, that whatever constituent 
or component lessens the power of self-repulsion in the parti- 
cles of the blood, lessens its fluidity, and consequently requires 
a greater propelling power. If sanguineous plethora exists in the 
system, both the heart and the lungs must increase their action 
in force and frequency in order to effect the circulation. A load of 
ingesta in the stomach, or feecal matter in the intestines, mechani- 
cally impedes respiration, by offering resistance to the contrac- 
tion of the diaphragm in inspiration, and to the abdominal mus- 
cles in expiration. 
The characters of respiration in health, in the quiescent state 
of the animal, consist of a regular, uniform, gentle, and easy 
movement of the flanks, belly, and ribs ; a placid rising and fall- 
ing of these parts, recurring in almost imperceptible succession, 
from four to eight times in a minute, and very nearly effected by 
the action of the diaphragm and the elasticity of the structures 
of the chest and lungs alone. By exercise these movements in 
the respiratory machine are increased in frequency and extent 
proportionate with the exertion of the animal, whether arising 
from the velocity of his speed, or his efforts to advance in draw- 
ing a load ; and the rapidity of respiration is capable of increas- 
ing in number as to exceed even that of the pulse itself, and yet 
subside gradually to its former state of tranquillity and repose 
without any injurious effect on any part of the respiratory appa- 
ratus. The extent to which quick respiration may be carried, 
and its continuation urged with impunity, depends upon the de- 
gree of resistance offered by the above-named impediments. 
The less the obstruction to the movements of the machine, the 
sooner the rapid breathing becomes tranquil. This is the charac- 
ter of respiration in an animal of vigorous health, and in which 
the resistance of the previously described opposing accumulations 
has been removed — a state commonly termed “ condition” or “ fit 
to go.” 
The inspiration and expiration are equal in the healthy horse in 
quick and in ordinary breathing, except the return of blood to 
the heart is very rapid, when there is occasional sighing. In this 
case the mutual balance, or proportionate number of the heart’s 
contractions to each respiration, is disturbed. Four pulsations to 
one respiration is the natural standard of relationship, and when 
this is interrupted proportionate derangement succeeds. When 
