DISEASES OF BONES 191 



What is Leontiasis ossea ? 



This represents a congenital hypertrophy where the facial 

 and cranial bones are hypertrophied. Seen in horses (so-called 

 hull heads) and in dogs. 



Bachitis (Rickets). 



What is rachitis ? 



A constitutional disease, primarily characterized by soft- 

 ening and distortion of the bones of young animals. 



What are the causes ? 



They are obscure. Some authors claim a specific infec- 

 tion ; others heredity, unhygienic conditions, a deficiency of 

 earthy salts in the food, etc. 



Describe the changes taking place in the rachitic hone. 



There is chronic hyperemia of all the bone-forming tis- 

 sues. The periosteum thus exhibits thickening in the bone- 

 forming layer, giving the bone a thick and heavy appearance. 

 The tissue proliferation arises in the osteogenous layer of the 

 periosteum, remains soft for a long time and is late to calcify. 

 The insertion of muscles are the best places to observe these 

 periosteal proliferations. An insufficient amount of lime 

 salts in the excessively developed cartilage at the epiphyseal 

 line, as well as the indiscriminate distribution among one 

 another of medullary tissue bone and cartilage, is a peculiarity. 

 These changes do not confine themselves to the epiphyseal 

 line, but may render the shaft of the bone distorted and soft 

 that it may be cut with a knife. 



What are the characteristics of a rachitic bone f 



Abnormal development at the epiphysis near articulating 

 surfaces, distortion of the long bones and vertebral column. 



