4O NORMAL HISTOLOGY. 



homogeneous, and possesses a definite width throughout its length, 

 although the several fibres forming the same net-work may vary in 

 thickness ; not infrequently slight triangular thickenings are found 

 at the points marking the union of several fibrils. Loosened from 

 their attachments, the elastic fibres assume a wavy, bent or coiled 

 condition, highly characteristic. Elastic fibres do not yield gelatin 

 when boiled, but contain elastin, which is probably enclosed within 

 a sheath of great delicacy, but of considerable resistance towards 

 reagents. 



The most immature, and morphologically the youngest, form of 

 connective tissue is mucous tissue, a typical example of which is 

 found in the jelly of Wharton, in the umbilical cord. Here the 

 stellate cells still retain their embryonal characters, and, by the union 

 of their processes, form a protoplasmic net-work throughout the 

 tissue ; the meshes of this net-work are occupied by a semi-gelatinous, 

 indifferent, and but slightly differentiated intercellular substance, 

 containing few fibres and occasional wandering cells. 



All gradations of density between the immature mucous and the 

 more resistant areolar tissue are supplied by the various stages of 

 development. Ordinary connective or areolar tissue, as found be- 

 neath the skin and in many other localities, comprises both white 

 fibrous and elastic tissue. The former usually occurs as wavy bundles, 



which interlace to form a felt-work of 

 varying compactness ; it is probable 

 that the bundles are confined by a 

 delicate sheath, strengthened by trans- 

 versely and spirally wrapped fibrils, 

 whose positions are marked as con- 

 strictions, after the treatment of the 

 bundles with acetic acid. The indi- 

 vidual fibrils composing the bundles 

 lie embedded within and held together 



Connective-tissue cells from young urn- by a Soft homogeneous gFOUnd-Sub- 



biiicai cord: processes of cells unite to stance, securely uniting them ; in the 



form protoplasmic net-work ; fibrous ele- . '" 



ments slightly developed. denser tissues the ground-substance 



contains intercommunicating cell- 

 spaces and canaliculi, the surrounding areas appearing as a homo- 

 geneous matrix. The elastic fibres, in varying number and size, 

 form a net-work throughout the tissue. The fixed connective-tissue 

 corpuscles lie embedded among or directly applied to the surface of 

 the bundles of white fibrous tissue, forming, in such cases, an im- 

 perfect wrapping or covering ; within the interfascicular clefts are the 

 wandering cells. 



The density of the tissue depends largely upon the amount and 



