48 THE CONNECTIVE TISSUES [CII. IV- 



joined together by their edges, but sometimes they are made of con- 

 densed ground-substance, not of cells, and in other cases again (as 

 in the cornea) they are of elastic nature. 



Jelly-like Connective Tissue. 



We have now considered connective tissues in which fibres of one 

 or the other kind predominate, and some in which the cells are in 

 preponderance. We come lastly to a form of connective tissue in 

 which the ground substance is in excess of the other histological 

 elements. This is called jelly-like connective tissue. The cells and 

 fibres scattered through it are few and far between. It is found 



FIG. 73. Tissue of the jelly of Wharton from umbilical cord, a, Connective-tissue 

 corpuscles ; 6, fasciculi of connective-tissue fibres ; c, spherical cells. (Frey.) 



largely in the embryo, notably in the Whartonian jelly, which sur- 

 rounds and protects the blood-vessels of the umbilical cord. In the 

 adult it is found in the vitreous humour of the eye. 



Various points in the structure of the tissue are illustrated in 

 figs. 58 (p. 40) and 73. 



The occurrence of large quantities of ground-substance in such 

 tissues has enabled physiologists to examine its chemical nature. 

 Its chief constituents are water, and one or more varieties of mucin, 

 with traces of proteid and mineral salts. 



