THE STRUCTURE OF THE LYMPHATIC GLANDS. 47 



in the lymphatics towards the centre of the gland. If it be exa- 

 mined in either direction towards the afferent or efferent branches, 

 it will be found to become thinner, and, at last, to be continuous 

 with the layer of flat epithelium scales of the extra-glandular 

 lymphatics. 



The anatomical relations of the membrane, and its layer of 

 nucleated particles, are identical with those which characterize 

 the primary cells or membrane, and the secondary or secreting 

 cells of certain glands. The oval vesicles in the substance of the 

 membrane are germinal spots or centres of nutrition, and the 

 membrane is a germinal membrane. I am inclined to believe 

 the spots on the membrane to be the sources from which the germs 

 of the nucleated particles of the thick layer are derived. These 

 spots are doubtless in a state of constant activity in all lymphatic 

 glands, but must be called into much more vigorous action periodi- 

 cally in the mesenteric glands, during the passage of the chyle. 

 If this be the case, these spots must exert a force by which matter 

 is abstracted from the blood which circulates in the neighbouring 

 capillaries, for the purpose of developing a steady succession of 

 nucleated particles. 



The arrangement in the substance of the lymphatic glands of 

 this highly developed portion of the lymphatic system of vessels, 

 or, in other words, the mode in which the afferent communicate 

 with the efferent lymphatics, I have found to coincide with the 

 account usually given of it. The terminal branches of the afferent 

 form a more or less dense network with the radicals of the effe- 

 rent lymphatics. The question which has been so often agitated, 

 as to whether cavities exist, intermediate between the two sets of 

 lymphatics, is not one of much importance. Some lymphatic 

 glands, as has frequently been stated, exhibit, after injection with 

 mercury, nothing but a mass of lymphatic vessels ; others, again, 

 a mass of apparently intermediate cells, and Cruikshank correctly 

 remarks, that occasionally, when the mercury first passes through 

 a gland, cells only may appear, but after the injection has been 

 pushed a little further, vessels full of mercury may suddenly pre- 

 sent themselves.* 



* Cruikshank. " The Anatomy of the Absorbing Vessels of the Human Body? page 82. 



