MINUTE ANATOMY OF THE LYMPHATIC GLANDS. 329 



Lastly, there are also found in certain organs composed 

 of connective tissue, as the peritoneum and pleura of Mam- 

 mals, and the mesentery and urinary bladder of the Frog, such 

 large accumulations of lymph corpuscle-like cells in the interior 

 of very vascular regions, as to cause them to present the great- 

 est similarity to the follicular tissues, though here, again, no 

 intimate relation to the lymphatic vessels is capable of be- 

 ing demonstrated. It is noticeable, however, that, in regard to 

 the chief division of the bloodvessels, these structures differ 

 from those of the lymphatic follicles proper ; for whilst in the 

 latter the main trunks are distributed upon the surface, the 

 arteiy occupies a central position in each follicle of the spleen, 

 so that these appear to represent a dilatation of the tunica ad- 

 ventitia : on the other hand, veins are altogether absent in the 

 interior of the splenic follicles. All these differences in the 

 arrangements of the vascular system are, however, insufficient to 

 justify us in attributing to these structures a function different 

 from that of the lymphatic follicles of the digestive tract ; they, 

 too, probably constitute centres of development for the lympha- 

 tic cells which are carried away from the splenic follicles, not 

 indeed by the agency of lymphatic vessels, but by other pas- 

 sages, as by the veins which form a very dense investing plexus 

 around them (Easier), and by the analogous structures of the 

 serous membranes consequent upon their communication with 

 the above-described cavities. 



THE LYMPH GLANDS, GLANDULE LYMPHATICS. 



Up to a very recent period, the structure of the lymphatic 

 glands was classed with those in which no efferent duct could 

 be discovered. The lymphatic vessels were seen to penetrate 

 the surface of the gland at numerous points, as the vasa affe- 

 rentia, and to emerge from the hilus of the gland as vasa 

 efferentia; but in the interior of these organs the lymph path, 

 especially in its relation to the glandular structure, was in the 

 highest degree obscure. His, in the first instance, and subse- 

 quently Frey and Teichmann, have furnished intelligible ac- 

 counts of their structure ; and although their descriptions cer- 

 tainly differ in some few points, it nevertheless appears to me 



