INFECTIOUS DISEASES. 537 
had been used on an animal suffering from variola, were used on a 
horse for a quittor operation and transmitted the disease, which 
developed on the edges of the wound. 
Symptoms.—There is a period of incubation, after an animal has 
been exposed, of from five to eight days, during which there is no 
appreciable alteration in the health. This period is shorter in sum- 
mer than in winter. At the end of this time small nodes develop at 
the point of inoculation and the animal becomes feverish. The horse 
is dull and dejected, loses its appetite, and has a rough, dry coat with 
the hairs on end. There is moderate thirst. The respirations are 
somewhat quickened and the pulse becomes rapid and full. The. 
body temperature is elevated, frequently reaching 104° or 105° F. 
within 36 or 48 hours from the appearance of the first symptoms. 
The visible mucous membranes, especially the conjunctive, are of 
a bright rosy red. In the lymphatic, cold-blooded,.and more com- 
mon horses these symptoms of fever are less marked; even with a 
comparatively high temperature the animal may retain its appetite 
and work comparatively well, but these cases, if worked and over- 
heated, are liable to develop serious complications. 
At the end of from three and a half to four days the eruption 
breaks out, the fever abates, and the general symptoms improve. 
The eruption in severe cases may be generalized; it may be confined 
to the softer skin of the nose and lips, the genital organs, and the 
inside of the thighs, or it may be localized 7 the neighborhood of a 
wound or in the irritated skin of a pair of greasy heels. It consists 
of a varying number of little nodes which, on a mucous membrane, 
as in the nostrils or vagina, or on soft, unpigmented skin, appear red 
and feel at first like shot under the epidermis. These nodes soften 
and show a yellowish spot in the center when they become pustules. 
The epidermis is dissolved and the matter escapes as a viscid fluid 
at first citrine and later cloudy and purulent, which dries rapidly, 
forming scabs; if these fall off or are removed they leave a little shal- 
low, concave ulcer which heals in the course of five or six days. In 
the softer skin if pigmented the cicatrices are white and frequently 
remain so for about a year, when the pigment returns. The lips or 
genital organs of a colored horse, if covered with a number of small 
white spots about the size of a pea, will usually indicate that the 
animal has been affected with the horsepox. 
At times the pustules may become confluent and produce large, 
superficial, serpentine ulcers on the membrane of the nostrils, around 
the lips or eyelids, or on the borders of wounds and in greasy heels; 
in this case the part becomes swollen, hot, painful, and is covered 
with a profuse discharge of matter. In this form there is frequently 
a secondary fever lasting for a day or two. 
