108 STUDIES IN ADVANCED PHYSIOLOGY. 



granules, probably secreted or excreted by the cartilage 

 cells, which granules later on in some way not yet under- 

 stood, fuse, forming the characteristic fibres. While most 

 cartilages have a membrane around them called the peri- 

 chondrium, such a membrane does not figure in any way as 

 it does in the formation of bone, but is here merely an en- 

 veloping membrane supplied, of course, with blood-vessels. 



Fig. 53. DEVELOPMENT OF ELASTIC TISSUE BY THE DEPOSITION OF ROWS OF ELASTIC 



GRANULES, 0, FINALLY FUSING INTO A PLATE-LIKE EXPANSION OF ELASTIC SUBSTANCE 



INDICATED AT P. (After Ranvier.) 



The method of origin of yellow elastic tissue just cited, 

 probably does not differ from the manner in which the con 

 nective tissues proper and the humors arise, save that in 

 these the corpuscles which have produced them may actu- 

 ally wander out and leave nothing but their product behind. 

 The supporting tissues being thus not directly composed of 

 cells, possess no physiological activity, and when once 

 formed probably remain entirely unaltered during life. The 

 various forms do not differ much in chemical composition, 

 except the yellow elastic, all yielding when boiled, a variety 

 of gelatine. Their similar nature is further indicated in the 

 fact that they replace each other easily. Thus, cartilages 

 are replaced by bone, and broken bones are sometimes 

 cemented together by the formation of cartilage. 



HYGIENE OF SUPPORTING TISSUES. 



In reference to the supporting tissues, little need be 

 said from the standpoint of their hygiene. It is, of course, 



