1090 



GENERAL ANATOMY OR HISTOLOGY. 



Development of Connective Tissue. Connective tissue is developed from 

 embryonic connective-tissue cells derived from the mesoblast. These cells, at 

 first rounded, become fusiform and branched, and ultimately become the con- 

 nective-tissue corpuscles. A mucinous intercellular substance or matrix, partly 

 formed from the cells themselves and partly from the lymph exuded by the 

 neighboring blood-vessels, gradually separates the cells. In the matrix the 



FIG. 615. Mucous tissue. 



fibres are deposited, probably under the influence of the cells, but not by any 

 transformation of the cell protoplasm. In the case of yellow elastic fibres, rows 

 of granules of elastin are first laid down, these eventually fusing to form the fully 

 developed fibre. 



1. Mucous tissue exists chiefly in the "jelly of Wharton," which forms the bulk 



of the umbilical cord, but is also found 

 in other situations in the foetus, chiefly 

 as a stage in the development of the con- 

 nective tissue. It consists of a matrix, 

 largely made up of mucin, irj which are 

 nucleated cells with branching and anasto- 

 mosing processes (Fig. 615). Few fibres 

 are seen in typical mucous tissue, though, 

 at birth, the umbilical cord shows consid- 

 erable development of fibres. In the adult 

 the vitreous humor of the eye is a persis- 

 tent form of mucous tissue, in which there 

 are no fibres, and from which the cells 

 have disappeared, leaving only the mucin- 

 ous ground-substance. 



2. Ketiform connective tissue is found 

 extensively in many parts of the body, 

 forming the framework of some organs 

 and entering into the construction of 



many mucous membranes. It is a form of connective tissue, in which the inter- 

 cellular or ground-substance has, in a great measure, disappeared, and has been 

 replaced by fluid. It is apparently composed almost entirely of extremely fine 

 bundles of white fibrous tissue, forming an intricate network, yet chemically 

 t yields, besides gelatin, a fresh substance, reticulin, The fibres are covered 

 and concealed by flattened branched connective-tissue cells, and these must be 



FIG. 616. Retiform connective tissue, from a 

 lymphatic gland ; most of the lymph-corpuscles 

 are removed. (From Klein's " Elements of His- 

 tology.") o, The reticulum. c. A capillary blood- 



