Etiology. 953 



ment animals became thinner and fragile, while such changes did not 

 occur if at the same time calcium carbonate was also ad'ded to the 

 oats. Finally Lane saw during an enzootic the disease disappear when 

 the food was made ridher in calcium and was mixed with bone meal. 

 The assertion of Elliot, according to which the extra-European 

 osteoporosis is a climatic disease which occurs principally in wet 

 regions, was not confirmed by experiences in the Transvaal. 



The hypothesis that the bone salts sufPer solution because 

 of the absorption of lactic acid from the intestinal canal 

 (Heitzmann) or owing to the accumulation of carbonic acid in 

 the blood (Rindfleisch) has at present hardly any adherents 

 (p. 935). 



Trophoneurotic disturbances were attributed a causal rela- 

 tion to osteomalacia by Fehling (1890). According to this 

 author an increased activity of the ovaries produces, by reflex 

 action, a hyperemia of the bones, which in its turn would lead 

 to softening of the bony substance. 



The hypothesis is based upon the favorable results obtained in women ill 

 with osteomalacia by extirpation of the ovaries and also upon the demonstration 

 of a so-called "physiological osteomalacia" in pregnant women which was made 

 by Hanau (1892). This author repeatedly found newly formed osteoid tissue in 

 the bones and in the Haversian canals of pregnant and lying-in women whose bones 

 were otherwise healthy. But it must be noted that Liithje failed to find any 

 changes in the phosphorus- and calcium -metabolism in castrated female animals, 

 and that Gracsanyi saw recovery occur equally in six affected cows, although only 

 two of them were castrated, all being fed alike. 



Honnicke (1906) is inclined to assume that osteomalacia 

 occurs on the basis of a thyroid gland affection and that the 

 disease represents a form of hyperthyreosis. (In two of his 

 cases in horses the thyroid gland was much enlarged.) 



In a rabbit that was fed with normal thyroid substance during, and for two 

 months after, pregnancy, Honnicke found a decided softening of the pelvic bones 

 and moderate cachexia, while two control animals, which were also pregnant, 

 remained well. 



Among predisposing causes pregnancy and lactation merit 

 first consideration (see p. 951), while racial differences are of 

 importance only in so far as the calcium requirements of 

 different species vary. In regions where osteomalacia occurs 

 enzootically, recently imported animals are more apt to acquire 

 the disease than the native ones. 



It is evident from these considerations that there are many 

 problems still to be solved in the etiology of osteomalacia, and 

 that osteomalacia is not a disease with a uniform etiology. 

 Especially the experiences in European countries do not admit 

 any doubt that calcium deficiency of the organism may be re- 

 eponsible for osteomalacia, but for certain cases another origin 

 cannot be denied (see p. 937), 



