OF VETERINARY MEDICINE. 233 



calcified osseous tissue with a new uncalcified osteoid tissue. The 

 bones become subject to frequent fracture and increasing de- 

 formity, while the patient becomes more and more feeble and a 

 profound cachexia comes on. Patient may die of exhaustion, 

 but much more commonly succumbs to pneumonia or to some 

 other intercurrent affection. 



The bones usually retain their lamellar arrangement and their 

 external and internal construction are alike histologically un- 

 changed, except that the great mass of bone is decalcincd and 

 the altered bone appears homogeneous, sometimes fibrous. The 

 decalcification usually begins at the periphery and extends in 

 toward the center. Some of the lacunar cells remain after de- 

 calcification but many die. As the disease progresses, the os- 

 teoid substance melts away and increases the spaces between the 

 columns of bony tissue. 



The marrow is frequently congested and may be hemorrha- 

 gic or pigmented, from previous hemorrhages. The bones are 

 so soft that they can be easily broken in two. Frequent frac- 

 tures occur and serve to deform the bone. The ordinary form 

 of the disease attacks the spinal column and thorax and spreads 

 to the limbs and head. The most interesting and important 

 changes occur in the pelvis, which yields to the pressure of the 

 spinal column and the thighs. It becomes wholly transformed, 

 making the bearing of young almost impossible. 



Fragilitis ossuun is a hardening of the bones to the extent 

 of brittleness and usually occurs in old animals. It is due to the 

 absorption of the animal matter and inflammation is usually the 

 cause. In this condition fractures are very easy to occur. 



RACHITIS. 



Rachitis or rickets is a degenerate softening of the bones 

 that occurs only in the young. It is due to some disturbance 

 that prevents the ossification of the bone. It is really a con- 

 stitutional disease and nutritional disorder. The lesion is charr 

 acterized by deficient calcification and increased absorption of 

 the bones, which in consequence are permanently altered in size 

 and shape. All the parts of the skeleton are affected. The 



