250 ABSORPTION LYMPH AND CHYLE 



The lymphatics are very elastic ; and it has been shown that the 

 larger vessels and those of medium size are contractile, although the 

 action of their muscular fibres, like that of all fibres of the non-striated 

 variety, is slow and gradual. 



An important point in connection with the anatomy of the lymphatic 

 vessels is the question of the existence of openings in their walls, which 

 might allow the passage of solid particles or of emulsions. Anatomical 

 observations have indicated the existence of stomata, of variable size 

 and irregular shape, in the smallest vessels ; and an argument in favor 

 of the existence of these openings is the fact of the actual passage, 

 through the walls of the vessels, of fatty particles, the entrance of 

 which can not be explained by the well-known laws of endosmosis. 

 The anatomical evidence of the existence of openings is derived mainly 

 from preparations stained with silver nitrate. It is assumed that silver 

 nitrate stains the solid parts of tissues and the borders of the endothelial 

 cells, and that non-nucleated areas which do not present any staining 

 are necessarily open. In preparations of the lymphatics, the solution 

 of silver is seen staining the tissues and especially the borders of the 

 endothelial cells lining the vessels ; but there are areas between these 

 cells where no staining is observed and in which no nuclei are brought 

 out by staining with carmin. 



Lymphatic Glands. In the course of the lymphatic vessels, are 

 small lenticular bodies, called lymphatic glands, or nodes. The number 

 of these is very great, although it is estimated with difficulty, from the 

 fact that many of them are very small and may escape observa- 

 tion. It may be stated as an approximation that there are six or seven 

 hundred lymphatic glands in the body. Their size and form are also 

 variable within the limits of health. They usually are flattened and 

 lenticular, some as large as a bean and others as small as a small pea 

 or even a pin's-head. They are arranged in two sets ; one superficial, 

 corresponding with the superficial lymphatic vessels, and a deep set, 

 corresponding with the deep vessels. The superficial glands are most 

 abundant in the folds at the flexures of the great joints and about the 

 great vessels of the head and neck. The deep-seated glands are most 

 abundant around the vessels coming from the glandular viscera. A dis- 

 tinct set of large glands is found connected with the lymphatic vessels 

 between the folds of the mesentery. These are known as the mesen- 

 teric glands. All the lymphatic vessels pass through glands before 

 they empty into the great lymphatic trunks, and most of them pass 

 through several glands in their course. 



The normal glands are of a grayish white or reddish color, of about 

 the consistence of the liver, presenting a hilum where the larger blood- 



