168 MANUAL OF HISTOLOGY. 



of the branched cells. Ranvier has described similar struc- 

 tures under the name "laches laiteuses." 



Development of fat-tissue. Their relation to the develop- 

 ment of fat-cells is of extreme interest. If we accept the views 

 of Klein and Flemming, the branched cells are converted into 

 fat-cells, and the former observer has pointed out that, by fol- 

 lowing up a perilymphangeal tract into a vascularized fat-tract, 

 we may find all stages of conversion into fat-tissue. The fat- 

 tracts are found in the same location as the perilymphangeal 

 tracts, that is, along the larger blood-vessels, and the greater 

 the number of the former the less there are of the latter. The 

 conversion of branched cells into fat-cells varies in different 

 animals, and in different membranes of the same animal, and 

 under different conditions of nutrition. The formation of lym- 

 phoid corpuscles, supposed to go on from the branched cells, 

 must cease, necessarily, when they become converted into fat- 

 cells, and it is found that they are, in fact, present in less num- 

 bers when the latter process is going on. Let us consider the 

 relations of these branched cells to the lymphatics. The larger 

 blood-vessels are usually accompanied by a lymphatic on each 

 side, which gives off branches at irregular intervals, finally 

 breaking up into a capillary plexus, which may ensheath the 

 accompanying blood-vessels, or even enclose a blood-capillary 

 plexus. When the latter exists in a perilymphangeal nodule, 

 the lymphatic capillary may apparently communicate directly 

 with the lacunsD and canaliculi, the endothelial cells compos- 

 ing the capillary being continuous with those which invest the 

 spaces, and covering externally, it may be, the blood-capillary 

 as well (Klein, Delaiield). 



Course and termination of the lymphatic radicles. In 

 tracing the lymphatic capillaries we find that they run in every 

 direction, branching irregularly, and vary in calibre and num- 

 ber in different parts. It is very difficult to trace one of them 

 to a positive termination. The interstices of the connective- 

 tissue fasciculi in brushed silver preparations sometimes pre- 

 sent an irregular shape, as if they were enclosed by irregular 

 cells. This appears to me to be often due to the convolutions 

 of the fasciculi, made more irregular, perhaps, by a cement 

 substance, or an interfascicular substance, either fluid or semi- 

 fluid, which has been coagulated by the processes following 

 death, and by the action of our reagents. The irregular action 



