vii CARTILAGE 115 



Thus connective-tissue consists partly of cells, but 

 between these and forming the main substance of the tissue, 

 is a matrix or intercellular substance, enclosing fibres. In 

 the embryo the tissue consists of closely packed cells, but, as 

 development proceeds, these separate from one another, and 

 the ground-substance is formed between them. 



Cartilage. The ordinary clear or hyaline variety of this 

 tissue is conveniently studied by examining a piece of the 

 thin edge of the omo- or xiphi-sternum, or by taking a thin 

 section with a razor of the head of the humerus or femur. 



Cartilage consists of a tough, elastic, transparent, homo- 

 geneous matrix (Fig. 34, in) containing numerous cavities 



FIG. 34. Section of cartilage, from the head of the frog's femur. 

 c. cells ; c'. cells undergoing fission ; c. s. empty cell-space ; m. matrix. 



or cell-spaces (c.s\ in each of which is a nucleated cell (c). 

 The cell-spaces, or lacunce, are in many cases arranged in 

 groups of two or four, sometimes close together, sometimes 

 with a narrow space of matrix or intercellular substance 

 between them. This is due to the fact that cartilage grows 

 by the cells undergoing binary fission, so that two cells are 

 formed in one cell-space : the two then gradually separate 



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