560 DISEASES OP THE HOESE. 



dietetic, and climatic conditions. It may occur in sporadic form, but 

 in certain regions, such as South Africa, Australia, Madagascar, 

 India, Hawaii, and in this country it seems to be enzootic, several 

 cases usually appearing in the same stable or on the same farm, and 

 numerous animals being affected in the same district. In the United 

 States the disease has been found in all the States bordering the 

 Delaware River and Chesapeake Bay, in some of the New England 

 States, and in many of the Southern States, especially along the coast 

 in regions of low altitude. In Europe the disease appears to be quite 

 rare, and is usually described as a form of osteomalacia, a disease 

 which is not uncommon among cattle of that continent. However, the 

 opinion that bighead is only a form of osteomalacia can not be ac- 

 cepted, nor can the infrequency of the former among European horses 

 and the frequency of the latter among other live stock be conceded on 

 the argument which has been presented, namely, that the better care 

 which horses receive prevents them from becoming affected. In the 

 Southwest, where osteomalacia, or creeps, has not infrequently been 

 observed by the writer among range cattle, no case of osteoporosis of 

 the horses using the same range has been noted, although the latter 

 animals are given no more attention than the cattle. 



The appropriate treatment of osteomalacia in cattle is so effective 

 that if osteoporosis were a similar manifestation of disease a similar 

 line of treatment should prove' equally efficacious. However, this is 

 not the fact. On the other hand, the occurrence of osteomalacia on 

 old, worn-out soil, or on land deficient in lime salts, or from eating 

 feed lacking in these bone-forming substances, or drinking water 

 with a lime deficiency, is in perfect accord with our knowledge of the 

 disease. But osteoporosis may occur on rich, fertile soil, in the most 

 hygienic stables, and in animals receiving the best of care and of 

 bone-forming feeds with a proper amount of mineral salts in the 

 drinking water. 



Cause. — The cause of this disease still remains obscure, although 

 various theories have been advanced, some entirely erroneous, others 

 more or less plausible ; but none of these has been established. Thus 

 the idea that feeding fodder and cereals poor in mineral salts and 

 grazing in pastures where the soil is poor in lime and phosphates will 

 cause the disease has been entirely disproved in many instances. 

 Others have considered that the disease starts as a muscular rheuma- 

 tism which is followed by an inflammatory condition of the bones, 

 terminating in osteoporosis. The idea that the disease is contagious 

 has been advanced by many writers, although no causative agent has 

 been isolated. Numerous experiments have been made by inoculating 

 the blood of an affected horse into normal horses without results. A 

 piece of bone taken by Pearson from the diseased lower jaw of a colt 

 was transplanted into a cavity made for it in the jaw of a normal 



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