THE ADIPOSE TISSUE. 45 



it is often called yellow elastic tissue. Its component fibres have re- 

 markably dark outlines ; they are never quite parallel to each other ; 

 they frequently branch and unite again ; and when torn, their ends 

 curl up, Fig. 18. In this form the elastic tissue exists in the two vocal 

 cords of the larynx, and in certain peculiar ligaments of the spine. 

 In the elastic coat of the arteries many of the fibres are flattened, and 

 join together so frequently as to form a very close network, Fig. 19, 

 a, or even a perforated membrane, Fig. 19, b. The elastic tissue is 

 neither very vascular nor sensitive. 



Adipose tissue or fat. This tissue consists of numerous roundish or 

 oval compressed vesicles, filled with an oily fluid and held in clusters 

 by minute bloodvessels, and by the filaments of the areolar tissue in 

 which they lie, Fig. 20. The fatty matter within the vesicles, though 

 fluid at the natural temperature of the body, become more solid as this 

 gets cool, and sometimes even partly crystallizes. In the state of 

 emaciation, the fat vesicles become shrivelled and emptied of oil. 



The fat acts as a filling or padding material in the body, between 

 other parts; it also serves to smooth and round the outline of the form ; 



Fig. 20. 



Fig. 20. Vesicles or cells of the adipose tissue or fat, supported by filaments of areolar connective tissue. 

 The cells are supposed to be filled with an oily fluid. Magnified 100 diameters. (Sharpey.) 



it acts as a non-conductor, by which heat is retained in the body ; and 

 it is a store of nutriment always available for use. It is more abun- 

 dant in children and in females, than in adults and males generally. 

 The circumstances causing it to vary in quantity will be hereafter dis- 

 cussed. Fat is never found within the skull, where its alternate accu- 

 mulation and disappearance might interfere with the functions of the 

 brain ; nor in the lungs, whose action it would impede ; nor in the 

 eyelids, whose movements it would hinder. 



The marrow of bones is chiefly a fine adipose tissue. Fat generally is 

 a very vascular texture ; but it is supplied with very few nerves indeed. 



Cartilage, fibro-cartilage, and yellow fibro-cartilage. Pure cartilage, 

 or articular cartilage, such as covers the ends of the bones at the joints, 

 is a firm, elastic opalescent substance, which consists of a homoge- 

 neous or faintly granular solid matrix, containing certain spaces in 

 which are imbedded the rounded or compressed bodies containing little 

 nuclei, and called cartilage cells or corpuscles, Fig. 21, a. Near the 

 free surface of a cartilage these corpuscles are flattened out, but deeper 

 they are arranged vertically, so that the cartilage splits more easily in 

 that direction. In the cartilages of the larynx and windpipe, in the 

 gristly part of the nose, and in the cartilaginous portion of the ribs, 



