STRUCTURE OF THE INTESTINE 



151 



receiving the central lacteals of the villi, pour their contents into a 

 plexus of large valved lymphatics which lie in the submucous tissue 

 and form sinuses around the bases of the lymphoid nodules. From 

 the submucous tissue efferent vessels pass through the muscular coat, 

 receiving the lymph from an intramuscular plexus of lymphatics, and 

 are conveyed away between the layers of the mesentery. 



FIG, 184. VERTICAL, SECTION OF A PORTION OF A PATCH OF PAYER'S GLANDS, WITH 

 THE LACTEAL VESSELS INJECTED. (32 diameters.) (Frey.) 



The specimen is from the lower part of the ileum : <r, villi, with their lacteals left white ; 

 b, some of the tubular glands ; c, the muscular layer of the mucous membrane ; d, cupola 

 or projecting part of the nodule ; e, central part ; /, the reticulated lacteal vessels occu- 

 pying the lymphoid tissue between the nodules, joined above by the lacteals from the 

 villi and mucous surface, and passing below into g, the sinus-like lacteals under the 

 nodules, which again pass into the large efferent lacteals, g 1 ; i, part of the muscular coat. 



Absorption of fat. The lymph-corpuscles of the villi are the chief 

 agents in effecting the passage of fat-particles into the lacteals. In 

 order to study this process of transference, it is convenient to stain 

 the fat-particles with osmic acid, which colours them black. It can 

 then be observed that in animals which have been fed with fat these 

 particles are present (1) in the columnar epithelium- cells ; (2) in the 

 lymph-cells ; and (8) in the central lacteal of the villus. The lymph- 

 cells are present not only in the reticular tissue of the villus, but also 

 in considerable number between the epithelium-cells ; and they can 

 also be seen in thin sections from osmic preparations within the com- 

 mencing lacteal ; but in the last situation they are in every stage of 

 disintegration. 



Since the lymph-cells are amosboid, it is probable from these facts 

 that the mechanism of fat -absorption consists of the following pro- 

 cesses viz. (1) absorption of fat into the columnar epithelium-cells of 

 the surface ; (2) inception of fat by the lymph-corpuscles in the epi- 

 thelium, partly from the epithelium-cells, and partly, perhaps, directly 



