536 Breeding and Management of Horses on a Farm. 
the body should be exposed to the action of the atmospheric air, 
by which a chemical change is effected, turning the venous or 
dark-coloured blood into arterial or florid blood, which alone is 
capable of carrying on life and supplying the different organs 
of the body with the stimulus necessary to their different actions. 
This change is effected in the lungs, where the blood is exposed 
to the operation of the air that is inhaled into them, and which 
fills the air-cells, in the delicate membrane of which the blood 
circulates. The arterial blood, in its transit through all parts 
of the body, is deprived of those vital properties which it has 
acquired from contact with the atmosphere, and becomes venous 
blood again, until it is once more propelled through the lungs 
and again arterialized. Venous blood contains a great quantity 
of carbon, and when from any cause (as, for instance, from the 
inhalation of charcoal) the chemical change in the blood so neces- 
sary to life does not take place, is found incapable of sustaining 
life, even for a very short period. Its first effects are upon the 
brain, which being deprived of the usual stimulus of arterial 
blood, becomes torpid, and thus the fountain-head of sensation 
being destroyed, voluntary motion is lost, the animal drops, and 
if not speedily relieved will die. 
If such be the effects of venous blood alone circulating for a 
very short time through the brain, we may very readily imagine 
that they will be perceptible in a minor degree when any circum- 
stance tends to limit the supply of arterial blood to that organ. 
As the loaded stomach, by impeding the action of the heart, 
deprives it of the power of propelling the blood with sufficient 
velocity and power through the various textures of the body, the 
circulation during repletion must be more languid than at other 
times ; among other organs the lungs, therefore, become gorged 
with blood, which passing but sluggishly through their substance, 
offer within a given period a less quantity than usual to the action 
of the atmospheric air, and consequently the slower the circula- 
tion the more the sup})ly of fresh arterial blood to every part is 
diminished. Hence it will not be difficult to conceive that the 
brain, while an animal is suffering from distension of the stomach, 
being but moderately supplied with fresh arterial blood, is com- 
paratively less energetic than at other times, its power of infusing 
vigour into the system and of rendering it capable of sustaining 
exertion of any kind is diminished, and the natural consequence 
is that state of torpor, lethargy, or somnolence to which repletion 
seldom fails to give rise ; and this state being found favourable to 
the deposition of fat between the various textures of the body, 
animals intended for llie butcher are constantly supplied with a 
large quantity of food in order that the inactive brain may rather 
conduce to repose than to exertion. 
