LECTURE II 

 BONES 



44. Osteology — the study of bones. Before entering, however, 

 into the details of the diseases and accidents peculiar to the bones 

 of domestic animals, I will first briefly run over the general skeleton. 



45. Bone may be defined as a yellowish-white, hard, ordinarily 

 insensitive substance, made up of two tissues, one of which is hard 

 or compact, the other being porous or cancellated ; while it is composed 

 of one-third animal and two-thirds earthy matter, and is covered by 

 a tough membrane called periosteum, and lined internally with a fine 

 membrane called endosteum. Bone is the basis of the animal frame, 

 or skeleton, giving attachment to the soft parts and shielding the 

 delicate organs. For descriptive 'purposes bones are divided into 

 three classes, as long, flat, short or irregular. 



46. Periosteum — the outer covering of bone — is a dense fibro- 

 vascular membrane consisting of two layers, an outer fibrous one 

 and an inner one of fine connective tissue which is continued into 

 the Haversian canals, by which means the bone is nourished. The 

 periosteum varies in thickness according to the position of the bone, 

 being thickest where the bone is most exposed to injury — for instance, 

 on the tibia and shank bone. 



47. Endosteum is a very fine vascular membrane lining the 

 internal or medullary cavities of the bones, wherein the marrow (a 

 fatty substance) is contained, and by its means the internal arteries 

 are distributed through the internal parts of the bones. The 



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