194 



MANUAL OF HISTOLOGY. 



Fig. 184.- A cell 

 from the reti- 

 cular connec- 

 tive - substance 

 of a lymphatic 

 gland, strongly 

 ramified. 



0*005 9- -0-0075 mm. They may, however, be met with more or less 

 granular. They are enclosed in a thin layer of a clear sub- 

 stance, forming the body of the cell, which is spread out 

 peripherally into a varying number of pale radiating pro- 

 cesses. These are primarily about 0*0023 mm. in diameter, 

 becoming, after a short course, three or four times as fine. 

 A secondary formation of branches is observed on these 

 processes rather frequently, which pass off usually more or 

 less at right angles. Further, there are generally formed, 

 by the union of such processes of adjacent cells, small 

 knots, in which naturally no nuclei are to be seen. The 

 meshes thus formed are usually of roundish or delicate 

 polyhedral figure (fig. 185), with a breadth of 0*0114- 

 0'0226 mm. The latter may, however, be much less, or, 

 on the other hand, more considerable; and meshes are found in certain 

 parts of far greater length and extent still. 



The whole of this delicate network, in 

 the fresh state, is very soft and fragile, and 

 only to be rendered perfectly visible on that 

 account by hardening treatment of the tis- 

 sue and removal of the lymph-corpuscles. 

 The connective-tissue cells withstand boil- 

 ing, but are, on the other hand, rapidly acted 

 on by alkalies and acetic acid. 



The genesis of this network of cells, and 

 of the lymph corpuscles enclosed in it, still 

 requires further investigation. 



US. 



The description of the cellular network of 

 reticular connective-substance just given, ap- 

 plies to its usual appearance in the system 

 at an early age. But we frequently encounter 

 in more mature bodies a certain change in 

 the tissue a shrivelling-up of the body of 

 the cell and nucleus so that these chief 

 central knots are only evident as slight 

 swellings at the corresponding points in the network. The appearance of 

 such portions has given origin to the mistake of confounding this cellular 

 network with which we are engaged with an interlacement of elastic fibres. 

 Fig. 186 gives a good idea of the structure of such a portion of tissue. 

 In it we may recognise also the characteristic relations of the reticular 

 connective-substance to the blood-vessels. Such a network, namely, is 

 always traversed by blood-vessels, in contradistinction to gelatinous tissue, 

 which is either very poor in the latter or entirely non- vascular. Eound 

 these vessels there is woven a secondary investing tunic, a microscopic 

 adventitia (a), formed by the union of neighbouring cells with their pro- 

 cesses and membranous expansion of the latter. 



This shrinking together of nucleus and cell-body may, moreover, give 

 place, under conditions of irritation, to a speedy increase in size again, 

 when we find, after a short period, the former plump appearance of both 

 restored. 



In other modifications of the cellular network a strong expansion 



Fig. 185. From a lymphoid follicle of 

 tne vermiform appendix of the rab- 

 bit ). Reticular tissue, with the 

 system of im-shes, b, and remains of 

 the lymph cells, a. Most of the latter 

 have been removed artificially. 



