208 E. CRESSWELL BABER. 



provided with valves, and their walls are formed by a layer 

 of endothelium, the cells of which are elongated, and have 

 a somewhat sinuous outline. Many of these cells appear to 

 be provided with two or even three oval-shaped nuclei. 



Coming off from these vessels, and traversing the gland in 

 all directions, are numerous lymphatic tuhes, of very varied 

 size and shape. The larger ones run principally between 

 groups of vesicles, and are in direct communication with 

 smaller ones, which pass between individual gland-vesicles. 

 The latter (the "few finer canals" of Frey), in a well-injected 

 specimen, are seen to be numerous, aiid are frequently noticed 

 partially, and not uncommonly completely, surrounding in- 

 dividual vesicles. The tubes vary very much in size and 

 form — in fact, they appear to adapt themselves accurately to 

 the intervals left between the vesicles. This being the case, 

 as might be expected, the diameter of a tube rarely remains 

 constant for any distance ; and where the intervals left 

 between the vesicles are larger the tubes expand into lym- 

 phatic spaces, having the most irregular shape. 



The lymphatic tubes, then, both large and small, together 

 with the lymphatic spaces, form a dense rounded network of 

 freely anastomosing canals, which permeates the entire sub- 

 stance of the gland. In no case have I seen any indication of 

 the lymphatics terminating in blind extremities, and cati only 

 attribute such an appearance to an imperfect injection. The 

 distinctly tubular character of the tubes, as well as the form 

 of the spaces and tubes generally, are best seen in specimens 

 injected with Berlin blue. In perfectly injected parts of silver 

 preparations a continuous layer of endothelial cells is seen 

 lining both larger and smaller lymphatic tubes and spaces 

 (see fig. 2). The endothelial cells are somewhat elongated, 

 and present an irregularly sinuous outline. They form a 

 delicate membrane, which in a thick section can be seen 

 following accurately the walls of the vesicles and covering 

 them like a thin veil. 



Once familiar with the appearances in preparations in 

 which an injection has been successful, the walls of the lym- 

 phatic tubes and spaces may be recognised between almost 

 all contiguous gland-vesicles in j)arts where the injection has 

 not penetrated. They appear in this case as two fine dark 

 wavy lines, studded at intervals with deeply-stained, staff- 

 shaped nuclei. This appearance, attributed to the lym- 

 phatics, may in some instances be produced by capillary 

 blood-vessels. Judging, however, from specimens in which 

 the lymphatics are injected, it is probable that we have to 

 do with such vessels, although it is not possible to distin- 



