CHAPTER II. 



DISEASES OF METABOLISM AFFECTING PRINCI- 

 PALLY THE BONES. 



RACHITIS. RICKETS. 



Definition. — Rachitis or rickets is a disease of young animals 

 characterized by faulty calcification of the growing bones and 

 impaired nutrition. 



Occurrence. — Rachitis exists in all parts of the world but is 

 much more common in Europe than in America. It is chiefly 

 seen among young swine and dogs. 



Etiology. — The real cause of rachitis is unknown. Want of 

 sunlight, impure air, confinement and lack of exercise are no 

 doubt important perdisposing factors. Several theories have 

 been advanced to explain the etiology of the disorder. Briefly 

 stated they are the following : 



(a) Infection producing a parenchymatous osteitis. The 

 sometimes enzootic occurrence, postmortem changes and a 

 similarity to the osteitis of phosphorus poisoning lend to 

 this theory some support. 



(6) Inanition due to feeding foods wanting in lime such as 

 potatoes, sour milk, bran, etc. Rachitis has been experi- 

 mentally produced in young animals by feeding them foods 

 poor in lime. 



(c) A disturbance in metabolism which induces an increase 

 in the elimination of lime from the body and a lessening of 

 the amount of lime to the bones. 



Necropsy. — Postmortem changes in rachitis are confined 

 largely to the epiphyses. They consist in a chronic hyper- 

 emia and inflammation of the bone with abnormal prolifera- 

 tion of the cartilages of the epiphyses. The quantity of lime 

 contained in the bone is deficient. As a result of the pro- 

 liferation the epiphyses become overdeveloped, the cartilage 

 formed being relatively too great in proportion to the bone. 

 Consequently the epiphyses are enlarged, distorted and the 



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