104 GENERAL ANATOMY OF THE TISSUES. 



here attain the great size of 004'"; and then contain, together 

 with a granular substance, many nuclei, and perhaps secondary 

 cells. 



2. As closed follicles, each of which consists of a membrana 

 propria with an epithelium upon its inner side, and has clear 

 contents : thyroidea. The follicles, which are not enlarged 

 cells, are surrounded by a large quantity of connective tissue, 

 and are united by it into smaller and larger lobules. 



3. As closed follicles, with a membrane of connective tissue, 

 and contents consisting of nuclei, cells and some fluid. Among 

 these I enumerate : 



a. The solitary follicles of the stomach and intestine; and 



b. The aggregated follicles of the small intestine, or Peyer's 

 patches (in animals those of the stomach and large intestine 

 also), both of which contain numerous blood-vessels in the 

 interior of the follicles. 



c. The follicular glands in the root of the tongue, the tonsils, 

 and the pharyngeal follicles, which in the walls of their sacs, 

 contain many closed follicles like those above mentioned, but, 

 so far as we as yet know, without vessels in their interior. 



d. The lymphatic glands, which appear to consist of follicles 

 like those of the Peyerian patches. 



4. As a cellular parenchyma, which contains numerous closed 

 follicles like those just described : Spleen. 



Fi 44 5. As racemose, aggregated, 



glandular vesicles opening into a 

 common closed canal or broad, 

 space, whose thick walls are 

 formed of a delicate investment 

 of connective tissue, and of a soft 

 substance consisting of many 

 nuclei and of vessels : Thvmus. 

 We know little of the chemical 



nature of these organs, which are 



all more or less richly supplied 



with blood-vessels. Those enumerated under 1, 2, 3, and 5, 



contain much protein and fat in their tissue, as also do the 



Fig. 44. A Malpighiau corpuscle from the spleen of the ox, x 150: a, wall of the 

 corpuscle ; b, contents ; c, wall of the artery upon which it is seated ; d, sheath of 

 the latter. 



