410 MANUAL OF HISTOLOGY. 



If a lymphatic gland from a new-born child be examined closely, it 

 will be seen that in some part of each nodal point in this network there 

 is a distinct cell-body, with a plump nucleus measuring 0'0045-0'0056 

 mm. in diameter. The breadth of the meshes is 0'0097 and 0'0160 mm., 

 but may rise to 0.0139-0.0226 mm. The cellular nature of the network, 

 however, may at other times be far less evident. 



In the adult we most usually meet with either a rudimentary shrunken 

 nucleus, or indeed none at all, in the but slightly thickened nodal points. 

 The openings of the meshes may be stated on an average to be O'OllS- 

 0'0194 mm. The septa may be fine or coarse, and vary in many respects. 



In the mammalian body the same appearances are presented in the 

 sustentacular matter, and similar varieties of the latter. 



]S"ow, though the structural relations just mentioned are easy of recog- 

 nition, the question as to the peripheral demarcation of the follicle 

 involves us in much difficulty. One thing is certain, namely, that they 

 .have no investing membrane. We may see, on the contrary, that the 

 cellular network, whose meshes are largest in the centre of the follicle 

 (fig. 399, b), becomes more dense towards the periphery (a), the meshes 

 which have been so far of roundish figure assuming the form of longi- 

 tudinal slits of considerable minuteness. The cellular nature of the net- 

 work is also more and more lost here, bands with numerous ramifications 

 being most abundant. Finally, on the surface of the follicle these fibres, 

 arranged like an elastic network of great denseness, envelope the former, 

 following all its curves (c). The small slits bounded by them usually 

 measure in their greatest diameter only 0-0081-0*0065 mm. Through 

 these small openings the passage of fluid, of fat molecules, and also of a 

 certain number of lymph-corpuscles may take place with great ease. 



As to the investing space spoken of above, it resembles, as we shall see 

 later on, that of many of Peyer's follicles. It may be observed surround- 

 ing every normally constituted follicle of the lymphatic glands, though 

 it disappears under many structural changes induced in these organs by 

 disease. It invests the whole follicle in the form of a perfectly continuous 

 transparent line, of by no means equal thickness, however, at all points 

 (fig. 398 ; and 399, i). Its breadth is usually about 0'0194-0'0303 mm. 

 and upwards. 



Within this space a varying number of lymphoid cells are to be seen. 

 If these be removed by brushing, a second tissue element then presents 

 itself, occupying the investing space, namely, a system of solid fibres (i), 

 which, springing from the internal surface of the capsule and sides of the 

 partitions, take a radial course towards the surface of the follicle, to be 

 inserted into the narrow meshed cellular network situated here. Thus, 

 taking their rise from the capsule and the surfaces of the septa, they hold 

 the follicle stretched and tense, as embroidery is fastened within a frame. 

 In consequence of this, collapse of the delicate follicular network is pre- 

 vented, and the fine slits in the surface of the latter are retained in an 

 open condition, provisions of importance as regards the lymph-stream and 

 the whole life of the organ. The retinacula in question present themselves 

 either in the form of non-nucleated, coarse or fine fibres, or bands, usually 

 giving off branches at an acute angle ; or there may occur in the nodal 

 points of the former nuclei showing that we have to do with a system of 

 cells. Here again we have presented to us the various forms of that so 

 varied group, the reticular connective-tissues. 



