43 ANATOMY OF THE LYMPHATIC SYSTEM. 



(trabeculse) small branches sprang in regular intervals, anastomosing 

 with each other and forming a mesh work. Seen from the surface 

 it looked exactly like a fenestrated membrane. The meshes were 

 occupied by those above-mentioned lymph-sinuses. 



In frogs the imagination does happen not only in that way, that 

 one of the blood-vessels or the nerve-trunk is invaginated in a 

 lymphatic vessel, but sometimes the whole trabecula which contains 

 the blood-vessels and the nerve-trunk is invaginated in a lymphatic 

 vessel. 



(fi) Besides those lymphatics which are to be found in and near 

 the chief trabeculae of the mesentery, there exist other lymphatic 

 vessels, which belong to that portion of the membrane which stretches 

 between the chief trabeculse. 



These are more or less wide vessels, provided with no valves ; their 

 wall is a single layer of rhombic endothelium with sinuous outlines. 

 They correspond to what is generally called lymphatic capillaries. 

 They accompany generally the smaller veins. In the pencilled silver- 

 stained mesentery of the dog, cat, monkey and frog they are very 

 easy to demonstrate. They are anastomosing with each other to a 

 wide net-work, and are also, like those previously-mentioned vessels, 

 provided with dilatation-sinuses. In those mesenteries where there 

 is little fat tissue, and consequently the tymphangial plaques and tracts 

 are clearly seen to consist of branched cells, it is also evident that 

 these patches and tracts have always on one or both their sides 

 lymphatic vessels. 



In the mesentery of living curarized toads prepared for Cohnheim's 

 experiment one can very often distinguish the lymphatic vessels with 

 great ease. In some places they form a rather scarce net-work of 

 vessels, which run along the blood-vessels ; in some other places they 

 break up in a dense system of lacunae. In several instances I have 

 found knobs of different size projecting into the lumen of the lymphatic 

 vessels from their endothelial wall. These knobs were seen to consist 

 of an accumulation of germinating endothelial cells ; and, in fact, I have 

 been able in one instance to observe that these germinating endothelial 

 cells detach themselves, and are carried away by the lymph-current. 

 I conclude from this that here a local germination of lymphoid cor- 



