DEVELOPMENT OF CARTILAGE. 



251 



pellucid substance, forming as it were a network of bright meshes inclosing them, 

 but in reality consisting of the cohering capsules of the contiguous cells, and 

 constituting all that exists of the matrix at this time. 1 Glycogen appears at an 

 early period in the protoplasm of cartilage-cells. Rouget found it in the sheep's 

 embryo of two months, both in ossifying cartilage and in the cartilages of the 

 trachea. 



The subsequent changes consist in enlargement and multiplication of the cells 

 and development of the intermediate matrix from a substance which is formed 

 around and between them. The process appears to be as follows (fig. 293) : The 

 cartilage cells first divide, a species of capsule being formed round each of the 

 young cells (B), whilst the old one inclosing them becomes blended with the 

 intercellular matrix, and after a time, is no longer traceable (c). The new cells, in 

 turn, divide in the same way, so as to make a group of four, each of which is 

 surrounded by its own capsule (D), whilst the capsules of the first descent 

 (secondary) blend with the matrix (E) like their predecessor. 



mmm 



Fig. 293. PLAN OF THE MULTIPLICATION OF CELLS OF CARTILAGE (Sharpey). 



A, cell in its capsule ; B, divided into two, each with a capsule ; C, primary capsule disappeared, 

 secondary capsules coherent with matrix ; D, tertiary division ; E, secondary capsules disappeared, 

 tertiary coherent with matrix. 



The four cells may each form a succession of capsules and thus become more 

 separated from one another, or they may divide again and form a group of eight 

 or more. It is by reason of the cells remaining in contiguity with one another 

 after the division is complete that the groups of corpuscles which are so charac- 

 teristic of cartilage are produced. 



. It is doubtful how the capsule is produced ; whether excreted by the cell which 

 it afterwards incloses, as held by Kolliker; or formed by conversion of a super- 

 ficial layer of the protoplasm of the cell-body, as was taught by Max Schultze ; or a 

 primarily independent deposit around the cells. However this may be, there is at 

 first no matrix but what is made up of the simple capsules. 



In further growth there is a difference, according as the cells do or do not 

 undergo frequent division. In the latter case a cell becomes surrounded by many 

 concentric capsules formed in succession ; that is, the first capsule is expanded, 

 and the others formed each within its expanding predecessor, so that the cartilage 

 comes to consist of scattered cells, each with a concentric system of capsules, 

 which by means of re-agents may be rendered visible in the neighbourhood of the 

 cells, but further off are inseparably blended into a uniform substance. When, 

 on the other hand, the cells have a tendency to frequent subdivision, the new 

 capsules are produced by the new cells, and are included in and finally blend 

 with those which had belonged to the previous cells, as shown by fig. 293. 



1 Cartilages, which retain this condition throughout life, have been termed " parenchymatous." An 

 example of this is found in the cartilage of the mouse's ear. 



