OSTEOPOROSIS, OR BIGHEAD. 561 



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 dis- 

 tricts, in one of which the rainfall is 150 inches annually, where big- 

 head 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 improve- 

 ment and frequently by recovery. In the wet district horses in both 

 good and bad stables take the disease, but in the dry districts no 

 unfavorable or unhygienic surroundings produce the affection. As 

 both native and imported 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 sug- 

 gested that the causative agent may only be transmitted by an inter- 

 mediate 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 always without result. We know 

 that coast fever is infectious, and that it can not be transmitted by 

 blood inoculations, but is conveyed with remarkable ease by ticks 

 coming from diseased cattle. That the cause has not been observed 

 may be accounted for by its being invisible even to the high magnifica- 

 tion of the microscope. 



On some farms and in some stables bighead is quite prevalent, a 

 number of cases following one after another. On one farm of thor- 

 oughbreds in Pennsylvania all the yearling colts and some of the 

 aged horses were affected during one year, and on a similar farm 

 in Virginia a large proportion of the horses for several years 

 were diseased, although the cows and sheep of this farm remained 

 unaffected. 



Symptoms. The commencement of the disease is usually unob- 

 served by the owner, and those symptoms which do develop are gen- 

 erally not well marked or are misleading unless other cases have been 

 noted in the vicinity. Until the bones become enlarged the symptoms 

 remain so vague as not to be diagnosed readily. The disease may be 

 present itself under a variety of symptoms. If the bones of the hock 

 become affected, the animal will first show a hock lameness. If the 

 long bones are involved, symptoms of rheumatism will be the first ob- 

 served, while if the dorsal or lumbar Vertebra? are affected indications 

 of a strain of the lumbar region are in evidence. Probably the first 

 H. Doc. 795, 59-2 36 



