THE CONNECTIVE TISSUES 



35 



in consequence is admirably adapted to fulfil various mechanical functions 

 in the body. It is, however, quite pliant, bending easily in all directions. 

 When boiled, fibrous tissue yields gelatin, a derivative of collagen. 



Elastic Tissue. The fibers of elastic tissue are usually associated in 

 varying proportions with the white fibrous tissue; but in some structures 

 as the ligamentum nuchae, the ligamenta subflava, the middle coat of the 

 larger blood-vessels the elastic fibers are almost the only elements present, 

 and give to these structures a distinctly yellow appearance. The fibers 

 throughout their course give off many branches, which unite with adjoining 

 branches to form a more or less close network. As the name implies, these 

 fibers are highly elastic, and are capable of being extended as much as 60 

 per cent, of their length before breaking. (See Fig. 9.) 



FIG. 8. CONNECTIVE-TISSUE 

 BUNDLES OF VARIOUS THICK- 

 NESSES OF THE INTERMUSCULAR 

 CONNECTIVE TISSUE OF MAN. 

 X 



FIG. 9. ELASTIC FIBERS OF THE 

 SUBCUTANEOUS AREOLAR TISSUE OF 

 A RABBIT. (After Schdfer.) 



Cartilaginous Tissue. This form of connective tissue differs from the 

 preceding varieties chiefly in its density. As a rule, it is firm in consistency, 

 though somewhat elastic. It is opaque, bluish-white in color, though in thin 

 sections translucent. All cartilaginous tissues consist of connective-tissue 

 cells embedded in a solid ground substance. According to the amount 

 and texture of the ground substance, three principal varieties may be 

 distinguished: 



i . Hyaline cartilage, in which the cells, relatively few in number, are embedded 

 in an abundant quantity of ground substance (Fig. 10, A.) The body of 

 the cells is in many instances distinctly marked off from the surround- 

 ing substance by concentric lines of fibers, which form a capsule for the 

 cell. Repeated division of the cell substance takes place, until the whole 

 capsule is completely occupied by daughter cells. The ground sub- 

 stance is pervaded by minute channels, which communicate on one hand 

 with the spaces around the cells, and on the other with lymph-spaces in 

 the connective tissue surrounding the cartilage. By means of these 

 channels, nutritive fluid can permeate the entire structure. Hyaline 

 cartilage is found on the ends of the long bones, where it enters into the 

 formation of the joints; between the ribs and sternum, forming the costal 

 cartilage, as well as in the nose and larynx. 



