486 MOVEMENTS. 



quite numerous, forming a close, anastomosing plexus, which 

 sends numerous small branches into the bony substance. 

 There is nothing peculiar in the arrangement of the veins. 

 The distribution of the veins in the bony substance has been 

 very little studied. 



The nerves of the periosteum are very abundant, and 

 form in its substance quite a close plexus. 



The adipose tissue is very variable in quantity. In some 

 parts it forms a continuous sheet, and in others the vesicles 

 are scattered here and there . through the substance of the 

 membrane. 



The importance of the periosteum to the nutrition of the 

 bones is very great. Instances are on record where bones 

 have been removed, leaving the periosteum, in which the 

 entire bone has been regenerated. The importance of the 

 periosteum has been still further illustrated by the remark- 

 able experiments of M. Oilier, upon transplantation of this 

 membrane in the different tissues of living animals. 1 



Physiological Anatomy of Cartilage. In this connec- 

 tion the structure of the articular cartilages presents the 

 chief physiological interest. The articular surfaces of all the 

 bones are encrusted with a layer of cartilage, varying in 

 thickness from -fa to -^ of an inch. The cartilaginous sub- 

 stance is white, opaline, and semitransparent when examined 

 in thin sections. It is not covered with any membrane, but 

 in the non-articular cartilages it has an investment analo- 

 gous to the periosteum. 



Examined in thin sections, cartilage is found to consist 

 of a homogeneous fundamental substance, marked with 

 numerous excavations, called cartilage-cavities, or chondro- 

 plasts. The intervening substance has a peculiar organic 



1 The original memoirs of M. Oilier were published in the Journal de la phys- 

 iologie, Paris, 1859-1863, tome ii., pp. 1, 169, 468, tome iii., p. 88, tome iv., p. 

 87, tome v., p. 59, and tome vi., pp. 466, 517. He has since published an elabo- 

 rate work on the subject, in two volumes. (Traite experimentale et dinique de 

 la generation des os, Paris, 1867.) 



