OSTEOPOKOSIS, OR BIGHEAD. 555 



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 •esta})lished. Thus the 

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

 in pastures where the soil is poor in lime and phospliates 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 

 ■horse, but without reproducing the disease. Petrone believes that the 

 Micrococcus nitrificans causes osteomalacia in man as a result of its 

 producing nitrous acid, which dissolves the calcareous tissues, and 

 when injected into dogs in pure culture a similar disease is produced. 

 It is probable that if this work is confirmed a somewhat similar causa- 

 tive factor will be discovered for osteoporosis. 



Elliott considers the latter disease to be of microbic origin due to 

 climatic conditions, and divides the island of Hawaii into two districts, 

 in one of which the rainfall is 160 inches annually, where bighead is 

 very prevalent, and the second of -which is dry and rarely visited by 

 rain, where the disease is unknown. Removal of animals from the wet 

 to the dry district is followed by immediate improvement and fre- 

 quently by recovery. In the wet district horses in both good and bad 

 stables take the disease, but in the dry district no unfavorable or unhy- 

 gienic surroundings produce the affection. As both native and im- 

 ported horses are equally susceptible, there is no indication of an 

 acquired immunity to be observed. 



Theiler has recently stated that his experiments in transfusing blood 

 from diseased to normal horses were negative, and has suggested that 

 the causative agent may only be transmitted by an intermediate host, 

 as in the case of Texas fever. He draws attention to this method of 

 spreading East African coast fever, although blood inoculations, as in 

 osteoporosis, are ^'^^'^^if^W^W^SO^ \^o^^ that coast fever is 



