CARTILAGE 



69 





cular membrane of dense fibre-elastic tissue. This membrane is the 

 pericliondrium. The inner portion of this membrane is richly supplied 

 with small cells, and it is from this cell layer, the chondrogenetic layer, 

 that the cartilage is presumably developed. 



The cartilage blastema is essentially mesenchyma. The chondro- 

 genetic cells of this p re cartilage multiply, and deposit about themselves 

 the structureless mass which first forms merely a capsule to the cell, 

 but which as it increases in amount, separates the various cells by 

 wider areas and becomes the cartilage matru: The cells, which in the 

 perichondrmm are small and 

 decidedly flattened, likewise in- 

 crease in size during this proc- 

 ess, and become more nearly 

 spherical, so that those cartilage 

 cells which lie near the center of 

 the cartilaginous plates are 

 spheroidal in shape, while those 

 toward the surface are more and 

 more flattened or elongated, 

 their long axes gradually re- 

 volving from a perpendicular 

 position in the center of the 

 plate to one parallel w 7 ith the 

 pericliondrium at the surface. 

 Each cartilage cell is inclosed 

 within a small space or lacuna. 

 which during life it entirely fills. 



Cell multiplication in carti- 

 lage is peculiar in that cell di- 

 vision occurs within a firm capsule and results in the formation of two 

 daughter-cells, which at first lie within the same encapsuled space. These 

 two cells may each again undergo division within the same space with 

 formation of four new cells. As a result of this peculiar method of cell 

 division the cartilage cells are arranged in groups of two, four, or even 

 eight cells. Each of the cells in the group deposits its capsule, and thus 

 forms a matrix about itself, so that the increasing space thus produced 

 between the cells of a group may separate them until they become com- 

 pletely isolated cartilage cells each within its own lacuna. In this way 

 the matrix of the cartilage is produced. Enlargement of n cartilage plate 

 occurs through a combination of interstitial and perichondrial growth. 



FIG. 82. CELLS AND MATRIX OF HYALINE 

 CARTILAGE FROM THE WALL OF A LARGE 

 BRONCHUS OF MAN. 



The grouping in pairs and fours, and the 

 tendency to produce a so-called 'capsule,' 

 are especially noticeable. Hematein. X550. 



