12 DISEASES OF THE HORSE. 
unable to pump the blood to the surface, and that the animal is on 
the verge of collapse. 
The skin is moist, to a certain degree, at all times in a healthy 
horse. This moisture is not in the form of a perceptible sweat, but it 
is enough to keep the skin pliable and to cause the hair to have a 
soft, healthy feel. In some chronic diseased conditions and in fever, 
the skin becomes dry. In this case the hair has a harsh feel that is 
quite different from the condition observed in health, and from the 
fact of its being so dry the individual hairs do not adhere to one 
another, they stand apart, and the animal has what is known as 
“a staring coat.” When, during a fever, sweating occurs, it is 
usually an indication that the crisis is passed. Sometimes sweating is 
an indication of pain. A horse with tetanus or azoturia sweats pro- 
fusely. Horses sweat freely when there is a serious impediment to 
respiration; they sweat under excitement, and, of course, from the 
well-known physiological causes of heat and work. Local sweating, 
or sweating of a restricted area of the body, denotes some kind of 
nerve interference. 
Swellings of the skin usually come from wounds or other external 
causes and have no special connection with the diagnosis of internal 
diseases. There are, however, a number of conditions in which the 
swelling of the skin is a symptom of a derangement of some other 
part of the body. For example, there is the well-known “stocking,” 
or swelling of the legs about the fetlock joints, in influenza. There 
is the soft swelling of the hind legs that occurs so often in draft 
horses when standing still and that comes from previous inflamma- 
tion (lymphangitis) or from insufficient heart power. Dropsy, or 
edema of the skin, may occur beneath the chest or abdomen from 
heart insufficiency or from chronic collection of fluid in the chest or 
abdomen (hydrothorax, ascites, or anemia). In anasarca or purpura 
hemorrhagica large soft swellings appear on any part of the skin, 
but usually on the legs, side of the body, and about the head. 
Gas collects under the skin in some instances. This comes from a 
local inoculation with an organism which produces a fermentation 
beneath the skin and causes the liberation of gas which inflates the 
skin, or the gas may be air that enters through a wound penetrating 
some air-containing organ, as the lungs. The condition here de- 
scribed is known as emphysema. Emphysema may follow the frac- 
ture of a rib when the end of a bone is forced inward and caused to 
penetrate the lung, or it may occur when, as a result of an ulcerat- 
ing process, an organ containing air is perforated. This accident is 
more common in cattle than it is in horses. Emphysema is recog- 
nized by the fact that the swelling that it causes is not hot or sensi- 
tive on pressure. It emits a peculiar crackling sound when it is 
stroked or pressed upon. 
