THE SUPPORTING TISSUES. 107 



other hand, the meshes being much more open, the enclosed 

 cells become much branched and have the power to move 

 about. Such wandering connective tissue corpuscles are 

 not always easily distinguished from wandering blood cor- 

 puscles. While in the case of cartilage the yellow elastic 

 varieties and the white fibrous varieties are found tolerably 

 separate, in the connective tissues we frequently find both 

 making up the framework of the structure in question. 

 Such a mixture of yellow elastic and white fibrous tissue is 

 called areolar tissue, and is particularly well exemplified in 

 the connective tissue under the skin. 



Humors. 



A final kind of supporting tissues frequently classed with 

 the connective tissues proper are the humors of the eye. In 

 these the matrix has never become hard with mineral de- 

 positions, has never developed fibres in it of any kind, but 

 remains almost perfectly liquid. The connective tissue 

 cells which have formed these humors, later on atrophy and 

 practically disappear, leaving this structureless matrix 

 behind. 



FORMATION OF CARTILAGE AND CONNECTIVE TISSUE. 



In their manner of formation all the supporting tissues 

 are alike. They are not made by a direct differentia- 

 tion of cells into these tissues, but, as stated once before, 

 are formed as a secondary product by the cells. In the 

 case of bone, this deposition has been treated at length. In 

 the remaining supporting tissues the origin is quite similar, 

 save that the cartilages and connective tissues are not added 

 continually from the outside, but grow throughout the en- 

 tire substance; that is, it is a growth by intussusception. 

 The cartilage cells in the matrix retain the power to divide, 

 and new cells formed by such division separate by the 

 secretion of more matrix between them. In the case of the 

 yellow elastic cartilage this has been specially worked out. 

 Here the matrix is first deposited in the form of little 



