THE BON 





.NTS. 



727 



scurvy, purpura, hiemorrhagic diathesis, and leukaemia. Clots of con- 

 siderable size between the periosteum and bone may lead to serious con- 

 sequences, by cutting off the blood supply to the superficial layers of 

 bone and thus inducing necrosis ; but when not liable to bacterial con- 

 tamination through contact with the air they are not usually of serious 

 import, and are readily absorbed. The smaller haemorrhages of the 

 medulla are not usually of much importance. The decomposition of the 

 extravasated blood may lead to extensive pigmentation of the marrow. 



HEALING OF WOUNDS AND FRACTURES OF BONE. 



The process of healing in bone after fracture is, when uncomplicated, 

 at first similar to that in ordinary healing by second intention in fibrous 



, . "^ ^-ST***?-****!^?* 1 ^- **> , '!> 



---^ -~-::, 









FIG. 479. NEW-FORMED CARTILAGE AND OSTEOID TISSUE FROM CALLUS AFTER FRACTURE OF THE FEMUR. 



tissue. The blood and other exudates and the tissue detritus are gradu- 

 ally absorbed or disposed of by phagocytes. By a proliferation of con- 

 nective-tissue cells of the region a larger or smaller mass of granulation 

 tissue is formed. This granulation tissue does not at first differ in 

 appearance from similar tissue formed elsewhere in the body in the 

 reparative phase of exudative inflammation. 



But soon, under the influence of the specially endowed cells of car- 

 tilage or bone or periosteum, but especially of the latter, the granulation 

 tissue becomes partially replaced either by cartilage, or by a substance 

 resembling bone in general appearance, but containing no lime salts. 

 This is called osteoid tissue. These new cartilaginous and osteoid tissues, 

 which are apt to occur together, form irregular masses or interlacing 



