210 



OP ABSORPTION AND SANGUIFICATION. 



FIG. 88. 



stomata or openings on the surface of the serous membranes leading into 

 lymphatic vessels, and forming therefore a communication between the 

 cavity of the serous sac and the interior of the lymphatic vessels, was de- 

 monstrated by the experiments of v. Reckliughausen and Dybkowsky, 

 and their characters and relations have been very carefully described by 

 Dr. Klein. He distinguishes two kinds, the true and the false. The true 

 are either the mouths of vertical lymphatic channels, which are lined by a 

 special layer of polyhedral cells containing granular protoplasm, and lead 

 into the lumen of a superficial lymphatic vessel, or they represent a discontin- 

 uity between the endothelium of the surface leading into a simple lymphatic 

 sinus near the surface, lined on one side only with epithelium. The false _or 

 pseudo-stomata are perpendicular processes which extend from the superficial 

 cells of the cell-network of the matrix of certain nodules, and pass up be- 

 tween the endothelial cells of the surface. 



151. The whole of the Lacteal Lymphatic system, with the serous cavities 

 in connection with it, may thus be looked upon as constituting one great 

 Assimilating Gland, dispersed through the body at large ; for it does not 

 differ in any essential particular from what the Kidney or the Testis would 

 be, if it were simply unravelled, and its convoluted tubuli spread through 

 the entire system, yet still all discharging their secreted products by a com- 

 mon outlet. In the cold-blooded Vertebrata, the Absorbent system appears 

 to attain a relatively greater development than it does in the higher classes; 

 but the difference really lies in the greater extension, in the former, of those 



glandular elements which are more 

 concentrated in the latter (see PpviNC. 

 OF COMP. PHYS., 184-187). Scat- 

 tered through the whole length of the 

 intestinal mucous membrane, from 

 the Stomach to the Rectum, are cer- 

 tain peculiar bodies, which are known 

 as Peyer's Glands. These may be 

 either "solitary" or " agmiuated ;" 

 the former being very generally dis- 

 tributed throughout the intestinal 

 canal, whilst the latter are restricted 

 to the small intestine, being most 

 abundant at the lower part of the 

 ileum. In whatever portion of the 

 canal they may occur, they are al- 

 ways limited in situation to that part 

 of its periphery which is opposite to 

 the mesentery. Each " Peyerian 

 gland," in a healthy mucous mem- 

 brane, presents the appearance of a 



circular, white, slightly-raised spot, about a line in diameter, over which 

 the membrane is usually less beset with villi, and is very often entirely des- 

 titute of them; and it is surrounded by a ring of openings, which are the 

 orifices of a set of crecal follicles disposed in a zone around it (Fig. 88). 

 The "Peyerian patches" (Figs. 88, 89) present aggregations of these spots, 

 varying 'in number from two upwards, but every one of their individual 

 components having precisely the same structure as the solitary gland. This 

 appears, from the researches of Briicke, Kolliker, and others, to be a sort of 

 capsule, whose walls are composed of indistinctly fibrillated connective tissue 

 with interspersed nuclei, and whose contents are thus but imperfectly differ- 

 entiated from the tissues in which the gland is imbedded. The contents of 



Portion of the mucous surface of the end of the 

 Human Ilc-iuu, moderately magnified, showing the 

 Peycrian Glands, the orifices of the follicles, and 

 the villi. 



