Ra ch His . Rickets . 569 



as in man, bad ventilation, close impure air, crowding, damp im- 

 pervious soils, and cold, are found more or less in places where 

 racliitis prevails. By lowering the general health and tone, these 

 debilitate the tissue cells and impair nutrition and growth. 



Confinement has a manifest influence. Rickets prevails in 

 children in the great manufacturing cities, where the ex- 

 clusion of sunlight and the breathing of impure air rob the system 

 of its vigor. The children of soldiers in India kept in close bar- 

 racks are largely rickety, while the more poorly fed native 

 children outside escape. Wild beasts in confinement are often 

 rachitic, unlike their fellows of the forest. Colts in confined 

 stables suffer while those in the fields and yards remain healthy. 

 Swine in Sweden in close pens and fed on potatoes alone suffer 

 (Stockfleth). 



Darkness usually coincides with confinement and it is note- 

 worthy that deep sea fishes, living in comparative darkness, have 

 usually cartilaginous skeletons. 



Infection. Certain facts seem to point to a direct infection, as 

 cooperating with the debilitating conditions above named. The 

 advent of tlie disease in England about 1700: its frequency in 

 English swine on the European continent (Schneidemiihl) ; and 

 its enzootic prevalence in different parts of America, give seeming 

 support to the doctrine. 



Dr. W. L. Williams has seen it appear on an Illinois farm 

 twenty years after reclamation from virgin prairie, prevail for ten 

 years and then disappear. There was a remarkable coincidence 

 of recurrent ophthalmia, and disease of the bones and joints 

 (navicular disease, spavin, splints, ring bones, etc.). 



In most of these cases the trouble occurred on low, damp 

 or impervii)us soils, agreeing witli rickets in children, which 

 avoids the Alps or hilly districts, and abounds in valleys or bot- 

 tom lands. 



Symptoms. The colts show a lack of thrift and though there 

 may be no lack of growth or size, they have a rough coat, a poor 

 development of the neck, arching of the back and drooping pel- 

 vis. The chest may seem to sink between the scapulae. They 

 move stiffly with swaying of the limbs, or even staggering and 

 are easily wearied or lacking in endurance. They lie a great 

 portion of their time or even persistently, refusing to rise. When 



