22 



INTRODUCTION. 



In the earliest phase, known as embryonic connective tissue 



(fig. 14, A), the cells are scattered, with long radiating processes, and 

 between the cells a thin gelatinous matter. It is by increase of this 

 intercellular substance by taking up water that many embryos gain so in 

 size without taking food. The embryonic connective tissue may de- 

 velop in various directions. 



-' . 



'^m ; \^ 



, 



: -. . . . ? \ 



'* 



A B C 



FIG. 14. Connective tissues. A, embryonic, from Amblystoma; B, expanded and con- 

 tracted pigment cells from Amblystoma; C, fibrous, from tendon. 



Thus some of the cells may contain 'pigment granules, forming 

 pigment cells (B), or oil globules may be deposited in them to such an 

 extent that the cells become spherical, while the intercellular substance 

 is reduced, thus affording fat or adipose tissue. Most common of 

 the connective tissues is fibrous tissue (white or non-elastic tissue) in 

 which the cells are branched or spindle-shaped while the matrix is 

 filled with fine fibrillae of considerable strength and little elasticity. 



These fibrillae are parallel to each other in tendons (C), which have to 

 convey strains in one direction; or they maybe interlaced confusedly, the 

 tissue then forming sheets or membranes. Occasionally, as between 

 the skin and the muscles, the fibrous tissue may be loose (areolar 

 tissue). In elastic tissue fibres of another kind are mingled among 

 the non-elastic fibrils. These are yellow and elastic, and when abun- 

 dant give an elastic character to the whole. 



In cartilage and bone the matrix is more solid and is abundant. 

 These are the skeleton-building tissues. In cartilage the matrix is 



