70 HISTOLOGY. 



out. The form of the cells corresponds accurately with that of 

 the spaces. In the preparation of the section the cells often 

 fall out, leaving the spaces empty. The part of the ground 

 substance immediately around the cell is highly refractive and 

 has a special affinity for certain stains. This is the so-called 

 cartilage capsule, and forms a boundary for the cartilage spaces, 

 containing the cells. The cells have in the beginning definite 

 cell membranes, which become thicker and firmer, and give rise 

 to the intercellular substance. The ground substance, then, is 

 a differentiated product of the cell protoplasm, and the most 

 lately formed ground substance is nearest the cells. The cap- 

 sule shows often a concentric marking. 



Inside the capsule there are often seen two cells, the result 

 of a division. Each of these cells forms a new capsule around 

 itself, which fuses with the capsule of the mother cell. As many 

 as four or eight cells may be seen in one capsule, forming a cell 

 group or family. These are separated only by a homogeneous 

 thin wall. There is in the formation of so large a group an 

 absorption of the inner layers of the capsule, in order to make 

 room for the cells. Such cell division inside a firm capsule we 

 call endogenous cell formation. 



The growth of cartilage takes place by an increase in the 

 number of cells and a further differentiation of new ground sub- 

 stance. These two processes we call interstitial growth. On 

 the surface the increase of cartilage takes place by the so-called 

 appositional growth, by which new layers of cartilage are formed 

 from the perichondrium. The interstitial growth takes place 

 mainly in young cartilage. 



The capsules are stained deeply, as above mentioned, by such 

 dyes as color mucin, while the rest of the ground substance 

 remains unstained. The capsule possesses also a great resistance 

 to the action of chromic acid and hydrochloric acid. By macera- 

 tion in these fluids the ground substance is dissolved and the 

 cartilage capsules remain for a time unchanged. 



That the ground substance is only apparently structureless 

 can be shown by the action of certain reagents (e. g., potassium 

 permanganate, 10 per cent, salt solution, trypsin, baryta- 



