470 DISEASES OP THE HOKSE. 



off, the surface bears a resemblance to the fine, yellow points of 

 miliary tuberculosis in the lung. The worm or its debris 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 fapid 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, arid 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 



^ Descazeaux has shown that the worms found in these summer sores are probably larval 

 forms of the stomach worms of the horse, Ilatronema megastoma, H. microstoma, and 

 B, musccB, Eansom has shown that the larval stage of H. muscw develops In the common 

 housefly, the fly becoming infested as a maprgot in horse manure. Infestation with the 

 adult worms in the stomach of the horse (PI. V, flg. 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 Hahronema 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 

 calls 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, fly- 

 control measures, and the use of clean bedding. — M. C. Hall. 



= 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. 



