76 



HUMAN ANATOMY. 



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iMStv 



Connective-tissue cells from cornea of calf which 

 occupy cell-spaces similar to those shown in preceding 

 figure. '' 525. 



as small bundles, which unite in all planes to form delicate net-works of great intri- 

 cacy. In lymphatic tissues, where the reticulum reaches a typical development, the 

 mesh-work contains the characteristic lymphoid elements and, in addition, supports 

 the superimposed stellate connective-tissue cells which formerly were erroneously 



regarded as integral parts of the fibrillar 

 Fig. 100. net-work. Reticular tissue, associated 



with fibrous and elastic tissue, is also 

 present in many other organs, as the 

 liver, kidney, and lung. This modifica- 

 tion of fibrous tissue differs from the more 

 robustly developed form in the absence 

 of the ground-substance and not yield- 

 ing gelatin upon boiling in water (Mall); 

 like fibrous tissue, the reticulum resists 

 pancreatic digestion. 



The development of fibrous tissue 

 has been a subject of much discussion re- 

 garding which authorities are still far from 

 accord. Two distinct views are held at 

 the present time ; according to the one, 

 the fibres appear within the originally 

 homogeneous intercellular matrix of the 

 early embryonal connective tissue without 

 the direct participation of the cells, the fibres being formed as the result of a process 

 somewhat resembling coagulation. This conception of the formation of the fibres of 

 connective tissue, known as the indirect mode, is held to account for the earliest 

 production of the fibrils in embry- 

 onic tissue. ^'^- ^°^- 



The other view, held by Flem- 

 ming, Reinke, and others, attributes 

 an active participation of the young 

 connective tissue cell, the peripheral 

 zone of its protoplasm, known as ex- 

 oplasm, being directly transformed 

 into fibrillae. In consideration of 

 the careful observations of Flem- 

 ming, it is now widely believed 

 that the method of formation of the 

 fibres of connective tissue directly 

 from the exoplasm of young con- 

 nective tissue cells is the usual one. 

 It is highly probable that the 

 connective tissue cells are concerned 

 in the production of the fibrous 

 tissue, since these elements become 

 much smaller as the formation of 

 the fibrous tissue advances. 



Elastic tissue usually occurs 

 as a net-work of highly refracting, 

 homogeneous fibres lying among the 

 bundles of fibrous tissue. The indi- 

 vidual fibres are much thicker than 

 the fibrillae of fibrous tissue and, 



although differing in width, maintain a constant diameter until augmented by fusion 

 with others. When disassociated, as in teased preparations, the elastic fibres assume 

 a highly characteristic form, being wavy, bowed, or coiled. The proportion of elastic 

 tissue in connective substances is, ordinarily, small ; in certain localities, however, as 

 the ligamenta subflava of man, or especially the ligamentum nuchfe of the lower 

 mammals, almost the entire structure consists of bundles of robust fibres of elastic 





Fibrous and reticular connective tissue from human liver after 

 pancreatic digestion. X 230. 



