THE LYMPHATIC SYSTEM. 167 



of the omentum which are seen to contain small patches are cut 



out and mounted A failure is more frequent than a 



success. Either the surface has not been pencilled enough, 

 and then the endothelium of both surfaces is colored, and 

 consequently, hardly anything is to be seen of the cellular 

 elements of the ground-substance ; or the surface has been 

 pencilled too hard, and then the arrangement of the ground- 

 substance is altered, its bundles appear considerably stretched 

 and distinctly fibrillar." 



When these patches referred to, found in the mesentery, 

 and particularly in the omentum, are examined, they are ob- 

 served, according to Klein, to consist of systems of somewhat 

 flattened, finely granular, nucleated, branched corpuscles con- 

 nected together ; the spaces which appear clear between them 

 forming the lacunae and canaliculi, corresponding to Reckling- 

 hausen's lymph canalicular system. The nuclei of these cells 

 are sharply defined, oval, and possess one or two nucleoli. 

 Lymphoid corpuscles are found in these spaces, and also 

 slightly larger corpuscles, which are supposed to be derived, 

 in part, at least, from the branched cells by a process of bud- 

 ding. Klein calls these patches lympTiangeal patches or nod- 

 ules, and lympTiangeal tracts. He divides them into two 

 classes. 



The perilympliangeal nodules or tracts which lie closely 

 connected with, but principally outside of, the lymphatic ves- 

 sels, are accumulations of more or less flat, branched cells, 

 which, by their growth and proximity to one another, make the 

 canaliculi shorter or close them entirely. The second class de- 

 velop within the lymphatic vessels, and are termed endolym- 

 pJiangeal nodules or tracts. They consist of those which 

 perfectly resemble adenoid or reticular tissue, and those which 

 are formed of a reticulum of branched cells, their spaces being 

 filled with liquid or a few lymphoid corpuscles. The last form 

 may have a rich blood-capillary plexus, and the branched cells 

 may possess buds, pedunculated and non-pedunculated, sup- 

 posed to represent different stages in the formation of a lym- 

 phoid corpuscle. These tracts and nodules are found most 

 frequently in the neighborhood of the blood-vessels and trabe- 

 culse. In young animals they are much less numerous and 

 more isolated than in adults, where they have become fused 

 into extensive tracts in consequence of the growth and division 



