Rachitis. Rickets. 577 



England's early activity on the sea, ajid the beginning of exten- 

 sive commerce and manufactures. From that time it has been 

 increasingly and extensively prevalent. Yet it has not been 

 shown to be propagated by any specific germ, nor to have extend- 

 ed in line with the introduction and use of new food products like 

 the potato. It appears to be traceable rather to unwholesome con- 

 ditions of life and a reduction of the general tone and nutritive 

 vigor. 



A deficiency of earthy salts in the food has been a natural and 

 favorite explanation, and the ill-health that is thereby brought 

 about is often an important factor. Yet rachitis occurs independ- 

 ently of such a condition. 



In Roloff's experiments, pigs fed on aliment deficient in lime 

 salts, suffered from bone softening, while the control animals on 

 food rich in lime salts remained well. The diseased animals 

 further recovered on a diet.rich in lime. Voight, Chossat, Milne- 

 Edwards, I/chman, Bousaingault, Heitzmann, etc., had similar 

 experimental results, and the effects were shown in goats, sheep 

 and dogs, in curvature, shortening, swelling of the costal carti- 

 lages and joints and contracted pelvis. Growing pigs have often 

 been found to suffer in this way when placed on an exclusive diet 

 of maize. The great improvement often secured in feeding an ex- 

 cess of calcareous phosphates tends to corroborate the hypothesis. 

 Wagner found that food rich in lime salts, and the administration 

 of small doses of phosphorus, rendered the epiphyses of the grow- 

 ing bones more compact. Kassowitz, on the other hand, found 

 that an excess of phosphorus caused absorption from the bone 

 substance and an irritable inflammation of the osseous tissue. 

 Schneidemiihl has seen the disease in calves raised on milk, poor 

 in lime, the product of emaciated cows ; in pigs getting only po- 

 tatoes and swill, and in puppies that were denied bones. It is 

 common in pigs on an exclusive diet of maize. Yet it is most de- 

 structive in many breeding studs where the alimentation is rich 

 and generous. It must be admitted that as a concurrent cause, 

 the paucity of lime salts and phosphates is a powerful factor, and 

 that in supplying the bone ash, and improving the nutrition, 

 these often prove of great value. Their privation is, however, 

 not an essential condition of rachitis. 



Free phosphorus. Ziegler and Kassowitz emphasize the hy- 

 37 



