130 LYMPHATIC SYSTEM. 



the cat and rabbit, the endothelium of the mesentery exhibits 

 pseudostomata of the same character as in the omentum. In 

 that of the toad and common frog, the trabeculae, in which the 

 large vessels run, split into a kind of meshwork of smaller 

 processes, the spaces of which are occupied by large lymphatic 

 sinuses, in which a beautiful endothelium with sinuous outlines 

 can be demonstrated by the silver method. 



Injection of Lymphatic Glands and of Mucous 

 Membranes. For the injection of the lymphatics of the 

 lymphatic glands, and of the mucous membranes, the " Einstich 

 Methode" (method of puncture) of Ludwig is the best. The 

 liquids used are either half per cent, silver solution or Prussian 

 blue. The animal to be employed must be perfectly fresh. A 

 very fine glass canula is used, which is connected either with a 

 syringe or with the apparatus described in the last chapter. 

 The method consists in penetrating any tissue in which there 

 are numerous lymphatics (e. g.< the submucosa of the mucous 

 membranes, the cortical substance of a gland, or the loose 

 tissue beneath the costal pleura), with a needle to a sufficient 

 distance. The needle having been withdrawn, the canula pre- 

 viously filled with the solution to be injected is introduced into 

 its track, and connected with the apparatus or syringe as the 

 case may be. The canula having been seized with ordinary 

 dissecting forceps, the liquid is injected. If it is seen that the 

 colored liquid is not contained in vessels but merely occupies 

 a bulging cavity in the tissue, the injection must be discon- 

 tinued as unsuccessful. In the case of the mesenteric or ingui- 

 nal glands of small animals, I succeeded in obtaining good 

 results with a tube drawn out at one end to a very fine point, 

 and bent near the point at right angles. This tube having been 

 filled with the liquid, was injected by the mouth. In the rabbit, 

 nothing can be easier than to insert such a tube into one of the 

 lymphatics of the mesentery, and in this way to inject the gland 

 to which it leads. Lymphatic glands, after injection, must be 

 placed in alcohol and used for the preparation of sections. 



Structure of the Lymphatic Vessels. The structure 

 of lymphatic vessels may be further advantageously studied in 

 those of the mesentery. In small cats or rabbits, it is easy to 

 prepare the parts of the mesentery in which there are abundant 

 lymphatic vessels leading to the mesenteric glands, by stretch- 

 ing them on cork and treating them with silver, after pencilling 

 away the endothelium of the peritonaeum with a camel-hair 

 pencil, moistened with serum. In these vessels, it is possible 

 to demonstrate the existence of transverse muscular fibres. 



Structure of the Lymphatic Glands. Mesenteric 

 Glands. The best glands for the purpose of study are those of 

 the -calf, ox, or cat. Small portions can be placed in Miiller's 

 liquid, or in solution of bichromate of potash. After a few 



