OR BIGHEAD. 563 



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 lilftly 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 are 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 in- 

 crease 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 

 Plaversian 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 knife, the 

 cut surface appearing finely porous. This porous area is soft, pliable, 

 and yields easily to the pressure of the finger. It has been shown by 

 chemical analysis that the bone of an osteoporotic horse, when com- 

 pared with that of a normal horse, shows a reduction in the amount 

 of fat, phosphoric acid, lime, and soda, but a slight increase in 

 organic matter and silicic acid. The bones lose their yellowish- 

 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 bones, 

 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 fre- 

 quently 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 tissue of the long 

 bones may contain hemorrhages and soft gelatinous material or 

 coagulated fibrin. The internal organs are usually normal, but a 

 catarrhal condition of the gastro-intestinal tract may be noted as a 

 result of the improper mastication, resulting from the enlargement of 

 the jaws and soreness of the teeth. 



Treatment. — The affected animal should be immediately placed 

 under new conditions, both as to feed and surroundings. If the horse 

 has been stable fed, it is advisable to turn it out on grass for two or 

 three months, preferably in a higher altitude. If the disease has been 

 contracted while running on pasture, place the animal in the stable 

 or corral. In the early stages of the disease beneficial results have 



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