INFECTIOUS DISEASES. 581 



rapidly, and if urged to go faster may sustain a fracture or have a 

 ligament torn from its bony attachments, especially in the lower 

 bones of the leg. An affected horse weighing 1,000 pounds was seen 

 by the writer to fracture the large pastern bone from rearing during 

 halter exercise. 



The animal becomes poor in flesh, the coat is rough and lusterless, 

 and the skin tight and harsh, producing a condition termed " hide- 

 bound," with considerable " tucking up " of the abdomen. The horse 

 shows a short, stilted, choppy gait, which later becomes stiffer and 

 more restricted, Avhile on standing a position simulating that in 

 founder is assumed, with a noticeable drop to the croup. The animal 

 at this stage usually lies down and remains recumbent for several 

 days at a time. Bed sores frequently arise and fractures are not 

 uncommon in consequence of attempts to arise, which complications, 

 in addition.to emaciation, result in death. 



The disease may exist in this manner for variable periods extend- 

 ing from two or three months to two years. The termination of the 

 disease is uncertain at best, but is likely to be favorable if treatment 

 and a change of feed, water, and location is adopted in the early 

 stages of the malady. 



Lesions. — As has been stated, the bones ai-e the principal tissues 

 involved. The nutrition of the bone is disturbed, as is indicated by 

 the diminished density or rarefaction of the bony substances, the 

 increase in the size or widening of the Haversian canal and the 

 medullary cavity, and the enlargement of the network of spaces in 

 the spongy tissue, the absorptive changes following the course of the 

 Haversian system. In this process of absorption there are formed 

 within the substance of the bone areas of erosion, indentations, or 

 hollow spaces of irregular shape.. These spaces increase in size and 

 become confluent, causing An appearance resembling some varieties 

 of coral. The affected bone may be readily incised with a Iniife, the 

 cut surface appearing finely porous. This porous area is soft, pli- 

 able, and yields easily to the pressure of the finger. It has been 

 shown by chemical analysis that the bone of an osteoporotic horse, 

 when compared with that of a normal horse, shows a reduction in 

 the amount of fat, phosphoric acid, lime, and soda, but a slight in- 

 crease in organic matter and silicic acid. The bones lose their yel- 

 lowish-white appearance, becoming gray and brittle. The affected 

 bones may be those of any region or portion of the body. Besides 

 the change already noted in the bones of the face, the ends of the 

 long bone,s, such as the ribs, are involved, and may be sectioned, 

 though not so readily as the facial bones. The bones of the vertebrae 

 are also frequently involved, necessitating great care in casting a 

 horse, as the writer has seen several cases of broken backs in casting 

 such animals for other operations. The marrow and cancellated 



