18 



PHYSIOLOGY OF FARM ANIMALS 



[CH. 



All cartilage consists of a matrix or ground substance con- 

 taining cells scattered within it. There are three principal kinds 

 of cartilage, hyaline cartilage in which the matrix is almost clear 

 and transparent, white fibro-cartilage in which the matrix con- 

 tains white fibres, and elastic fibro-cartilage in which elastic fibres 

 are present. 



Bone is a form of tissue produced by the ossification of con- 

 nective tissue. It may be divided into two classes according to 

 its origin, cartilage bone and membrane bone. Bone of the 

 latter kind is formed by the deposition of lime salts in the 

 ground substance of embryonic connective tissue. In this way 

 such bones as the maxillary bone are produced. Cartilage bones 



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V. 



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Fig. 12. Compact tissue of bone (after Sharpey from Gray). 



(e.g. the limb bones) are formed through the activity of the 

 cartilage cells. These become enlarged and arranged in rows, 

 and give rise to fibrous lamellae which afterwards undergo calci- 

 fication. The tissue becomes excavated by small holes through 

 which blood vessels, arising from the periosteum or covering 

 vascular membrane, pass into and through the bone. A fuUy 

 formed bone is seen to be composed of lamellae, consisting of 

 fine fibres which are calcified, lying in a matrix which is also 

 calcified, and contains the bone corpuscles or cells of the tissue. 

 Bone may be either compact as in the shaft of a long bone (e.g. 

 the femur) or cancellous as in the ends of such a bone. In com- 



