20 FIBRES; CONNECTING TISSUE. 



more irregularly. In studying the cells in tendon, 

 both longitudinal and transverse sections must be 

 examined, in order to see them well ; their branching 

 disposition can be clearly recognised only in the 

 latter. (PL III. fig. IV. 3.) 



Plasmatic cells are most advantageously studied, 

 however, in the cornea ; its entire substance, between 

 the two layers of epithelium which invest its anterior 

 and posterior surfaces, consists of an amorphous ma- 

 terial in which we find myriads of star-shaped cells 

 arranged in regular concentric lines running parallel 

 with its surfaces. The numberless branches given 

 off by the cells, on every side, anastomose in such a 

 manner as to form a very beautiful network. Very 

 dilute acetic acid must be applied to the section under 

 examination ; if the acid is too strong the branches of 

 the cells are rendered invisible, and the cells them- 

 selves appear simply fusiform, or spindle-shaped. (PI. 

 II. fig. V.) 



In the way of normal development, these plasmatic 

 cells may transform themselves into cartilage cells, as 

 in some tendons in old age, the inferior extremity of 

 the tendo achillis, for example, and the cartilaginous 

 enlargement of the peronceus longus, where it plays 

 over the cuboid bone. This transformation is effected 

 by the disappearance of the branches of the cell, and 

 the production of an external envelope, which thickens 

 into cartilage. (PI. IV. fig. I. 2 ; fig. II. 2.) 



They are metamorphosed in a like manner, in the 

 periosteum, into bone cells, by investing themselves 

 with a coating of earthy salts ; it is also through the 

 agency of these cells that layers of new bone are de- 



