26 PRINCIPLES OF VETERINARY SURGERY 



change into bone, fibrous tissue into cartilage, etc., by a 

 transformation of the matrix in each case. (Hektoen.) 



CARTILAGE. — The formative cells or chondroblasts 

 generally originate in the periosteum or perichondrium, the 

 medulla of bone, and sometimes in fibrous connective-tissue. 

 The cells secrete a homogeneous intercellular substance 

 which gradually encroaches upon them and they become 

 compressed into small spaces. This substance may remain 

 hyaline, or it may develop white or elastic fibres in its mat- 

 rix. Cartilage does not easily regenerate. Some deny that 

 it does at all. More often wounds of cartilage are repaired 

 through the formation of fibrous connective tissue which 

 forms a scar. 



BONE. — Osseous tissue undergoes as perfect a regenera- 

 tion as any tissue of the body through the calcification and 

 subsequent ossification of an embryonal tissue' known as 

 callus. The formative cells or osteoblasts arise from the 

 periosteum, perichondrium and bone-marrow. These grow 

 intO' the blood-clot which forms in a fractured or amputated 

 bone, and produce a large mass of granulation tissue, the 

 callus. This is purely connective tissue at first, but later 

 changes into cartilage and then into bone, by metaplastic 

 processes similar to those in the original formation of bone. 

 The callus forms a temporary bridge to hold the broken 

 fragments together until the process of cicatrization in bony- 

 tissue takes place. 



As early as the second day after a wound in osseous 

 tissue, the lacerated periosteum, muscles and blood-clot 

 are infiltrated with leucocytes. At some distance from 

 the immediate neighborhood of the fracture, the cells of 

 the periosteum, especially of the osteogenic layer, swell 

 up and multiply. Numerous angular and stellate cells, the 

 osteoblasts, appear and at the same time an active pro- 

 liferation of connective tissue cells begins in the medul- 



