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 conjunctivae, 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 in 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. 



