54 CONNECTIVE TISSUE CARTILAGE BONE 



cal with mesenchyma; from the viewpoint of progressive differentiation 

 it properly heads the list of connective tissues. 



Mucous Connective Tissue. Mucous, gelatinous or mucoid connec- 

 tive tissue occurs only in the umbilical cord, where it forms the 'jelly of 

 Wharton,' and in the vitreous humor of the eye. Its semifluid ground 

 substance is of a gelatinous consistence and forms the greater portion of 

 the tissue; in the vitreous humor there is little else. 



The cells are mostly of the branched lamellar variety, are few in imm- 



FIG. 62. GELATINOUS CONNECTIVE TISSUE FROM THE UMBILICAL CORD OF A XEW- 

 BORN INFANT. 



Safranin and water blue. X 410. 



ber in the vitreous, but more abundant in the umbilical cord. In the 

 vitreous humor also, there arc very few fibers; those which are present 

 are very line and form a delicate reticulum. In the umbilical cord the 

 fibers are more abundant, and possess a tendency to form bundles which 

 are disposed in parallel cylindrical layers around the large blood- 

 vessels. Elastic fibers are wanting. This type lacks also nerves, blood- 

 vessels and lymph-vessels; the two large umbilical arteries and the 

 umbilical vein have no vascular connection with the mucous tissue of 

 the cord. 



The essential chemical body in mucus is mucin, a glycoproteid. The 

 most typical mucous substance is the secretory content of goblet cells. 

 The mucus of embryonic and gelatinous connective tissue is closely 



