40 ANATOMY OF THE LYMPHATIC SYSTEM. 



extent with the pencilling. In the puppy, the pencilling is easier : 

 the membrane is not too tender, and therefore one succeeds much better 

 in obtaining a silver preparation in which the lymphatic system may be 

 successfully studied. 



What I shall describe hereafter refers only to a small extent to 

 silver preparations of the normal membranes ; to a greater extent it 

 refers to the investigation of fresh normal membranes, and chiefly to 

 the investigation of membranes either fresh or silvered that have 

 been slightly chronically inflamed. The latter, if the chronic in- 

 flammation has not reached too high a degree, are especially well 

 adapted for the study of the lymphatic system, for the simple reason 

 that here the lymphatics are held distended, either by the fluid of 

 oedema or by lymphoid corpuscles. Thus the tuberculous omentum 

 and pleura mediastini of the guinea-pig and ape have been of great 

 service in many cases in consequence of the oedematous condition. 



The lymphatic vessels which accompany the larger blood-vessels 

 have quite the same relation as we have found them to have in the 

 rabbit, i.e. they accompany each vessel either singly, or more frequently 

 in pairs, and are in a few cases of an invaginating character ; the latter 

 condition, however, being, on the whole, not very frequent. Con- 

 cerning their structure, there is to be made out only a wall composed 

 of endothelium ; they follow exactly the course of the venous branches ; 

 here and there also a lymphatic is seen beside an artery. As regards 

 those nodules and cords which, by their stroma, may be interpreted 

 as peri-lymphangial nodules and cords, there exists quite the same 

 condition as we have already determined for the omentum of the 

 rabbit ; namely, the lymphatic vessel terminates as such and loses 

 itself into the densely-aggregated lymph-canalicular system, while 

 the corresponding system of branched cells is in direct continuity 

 with the endothelium of the lymphatic vessel. Here, also, we find 

 amongst the tracts of lymph-canalicular cells which accompany some- 

 times a small vascular trunk simple lymph-lacunae, that is, a fusion of 

 several lymph-canaliculi. As in the rabbit, such simple lymph- 

 lacunse occur also quite superficially in the omentum and pleura 

 mediastini of the before-mentioned animals. Considerably often, 

 also, lymph-sinuses, viz. .sacciform dilatations of lymphatic vessels are 



