THE CONNECTIVE TISSUES. 



placed quadrate elements are seen in tendon, while sheets of flattened 

 endothelioid plates characterize basement-membranes and envelop 

 the bundles of fibrous tissue. 



In the denser structures the cells occupy spaces within the 

 ground-substance ; these spaces usually communicate directly with 

 one another by means of minute channels, or canaliculi, and form a 

 complicated system of "juice-canals" through the entire tissue. 

 Within these tissue-spaces, or lacuna, lie the connective-tissue 

 corpuscles, generally only partially filling the cavities, and being 

 usually especially applied to one wall of the space after the manner 

 of an endothelial covering. These interfascicular clefts within the 

 ground-substance may be regarded as the radicles of the lymphatic 

 system, in some localities, as in the peritoneum, standing in close 

 relation with both the lymphatic and the blood channels. 



The intercellular or fibrous constituents of connective tissue are of 

 two kinds white fibrous and yellow elastic tissue. "White fibrous 

 tissue ordinarily occurs as wavy bundles of varying thickness, com- 

 posed of silky fibrils of such fineness that, under ordinary amplifica- 

 tion, they present no appreciable thickness ; these bundles sometimes 

 run parallel, as in tendon, but more frequently interlace, forming 

 coarser or finer mesh-works, as seen in the omentum and subcu- 

 taneous tissues. When examined after teasing, the ultimate fibrils 



of the white fibrous 



FIG. 41. 



tissue appear as a 

 confused mass of 

 delicate interlacing 

 lines, but in their 

 undisturbed relation 

 they lie parallel, 

 whatever may be the 

 general disposition of 

 the bundles. Fibrous 

 tissue_jyelds gela- 

 tin on boiling in 

 water, and swells up 

 and becomes in- 

 distinct on treat- 

 ment with acetic acid. 

 Yellow elastic 



FIG. 40. 



tissue, on the con- 



White fibrous tissue : Elastic fibres isolated ; from the ad- 

 one end of the bundle has ventitia of the aorta. (After Schief- 

 , OCCUrS USUally been teased to display the ferdecker.) 

 33 a net-WOrk Of dis- component fibrilla. 



tinct fibres lying among the bundles of the white fibrous tissue. 

 Examined in detail, the elastic fibre appears highly refracting and 



