470 DISEASES OF THE HORSE. 
off, the surface bears a resemblance to the fine, yellow points of 
miliary tuberculosis in the lung. The worm or its débris is found in 
the center of such masses. These sores are very obstinate, resisting 
treatment for months in summer, and even after apparent recovery 
during the cold season they may appear anew the following summer. 
In bad cases the rubbing and biting may cause exposure of synovial 
sacs and tendons, and cause irremediable injury. Even in winter, 
however, when the diseased process seems arrested, there remain the 
hard, firm, resistant patches of the skin with points in which the 
diseased product has become softened like cheese. 
The apparent subsidence of the. disease in winter is attributed to 
the coldness and comparative bloodlessness of the skin, whereas in 
summer, with high temperature, active circulation, and rapid cell 
growth, inflammation is increased, itching follows, and from the 
animal rubbing the part the irritation is persistently increased. The 
hotter the climate the more troublesome the disease.* 
Treatment consists, first, in placing the animal in a cool place and 
showering the surface with cold water. The parasite may be de- 
stroyed by rubbing the surface of the wound with iodoform and 
covering it with a layer of collodion, and repeating the applications 
every 24 hours for 15 days, or until the sores heal up. Ether or 
chloroform, poured on cotton wool and applied to the sore for two 
minutes before painting it with collodion, may be used in place of 
iodoform.? 
CRACKED HEELS (SCRATCHES, OR CHAPS ON KNEE AND HOCK). 
This usually sets in with swelling, heat, and tenderness of the hol- 
low of the heel, with erections of the hairs and redness (in white 
skins), with stiffness and lameness, which may be extreme in irritable 
horses. Soon slight cracks appear transversely, and may gain in 
depth and width, and may even suppurate. More frequently they 
1 Descazeaux has shown that the worms found in these summer sores are probably larval 
forms of the stomach worms of the horse, Habronema megastoma, H. microstoma, and 
H. musce. Ransom has shown that the larval stage of H. musce develops in the common 
housefly, the fly becoming infested as a maggot in horse manure. Infestation with the 
adult worms in the stomach of the horse (PI. V, fig. 4) may take place through the inges- 
tion of such infested flies, or by the escape of the larva from the proboscis of the fly as 
it feeds on the moist lips of the horse. In view of this it may be surmised that summer 
sores may arise as the result of flies so infested feeding on the moisture on the skin of the 
horse. In some forms of summer sores along the abdomen there are found immature 
stages of Habronema which apparently have just escaped from the egg and which are 
younger than some of the stages found in the fly. In this case it is surmised that these 
embryos from the manure enter the soiled skin of the horse, as it lies down on dirty bed- 
ding and manure, and develop in the skin as they would ordinarily in the fly. Descazeaux 
ealls these summer sores cutaneous habronemiasis. 
Preventive measures consist in the removal of the adult worms from the stomach of 
the horse by the use of anthelmintics, the destruction of the embryos in the manure. fiy- 
control measures, and the use of clean bedding.—M. C, Haun. 
2 Descazeaux recommends the application and injection of 2 to 3 per cent trypanblue, 
though he states that the only truly efficacious treatment is the early and complete abla- 
tion of the invaded tissue.—M. C. H. 
