32. 



VETERINAEY PHYSIOLOGY 



and here strands of white fibrous tissue with little islands of 

 hyaline cartilage are found. It is also found when white 

 fibrous tissue, as tendon, is inserted into hyaline cartilage, 

 and is really a mixture of two tissues white fibrous tissue 

 and cartilage. 



4. Bone. The great supporting tissue of the adult is BONE. 

 (1) DEVELOPMENT AND STRUCTURE. Bone is formed by a 

 deposition of lime salts in layers or lamellae of white fibrous 

 tissue; but while some bones, as those of the cranial vault, face, 



and clavicle, are produced 

 entirely in fibrous tissue, 

 others are preformed in car- 

 tilage, which acts as a scaf- 

 folding upon which the for- 

 mation of bone goes on. 



Infra - membranous Bone 

 Development. This may be 

 well studied in any of the 

 bones of the cranial vault 

 where cartilage is absent 

 (fig. 12). 



At the centre of ossifica- 

 tion the matrix between the 

 fibres becomes impregnated 

 with lime salts, chiefly the 

 phosphate and carbonate. 

 How this deposition takes 

 place is not known ; and 

 how far it is dependent on 

 the action of cells has not 



1 



FIG. 12. Intru-membranous Bone Develop- 

 ment in the lower jaw of a foetal cat. 

 Above, the process of ossification is seen 

 shooting out along the fibres, and on the 

 lower surface the process of absorption is 

 going on. Two osteoclasts large multi- 

 nucleated cells are shown to the left. 



been clearly determined. As a result of this, the con- 

 nective tissue cells get enclosed in definite spaces, lacunae, 

 and become bone corpuscles. Narrow branching channels 

 of communication are left between these lacunae, the 

 canaliculi. This deposition of lime salts spreads out irregu- 

 larly from the centre into the adjacent fibrous tissue, and 

 this advance is preceded by a line of actively growing cells, 

 sometimes called osteoblasts. The fully formed adult bone, 

 however, is not a solid block, but is composed of a compact 



