226 



INTESTINAL DIGESTION. 



face of the mucous membrane of the intestine. Their secretion 

 is mucus having a slightly alkaline reaction, but it has never been 

 successfully obtained so pure as to admit of its being analyzed. 

 These glands are so few in number, comparatively, that their prod- 

 uct cannot be very abundant nor very 

 important in its action upon the food, 

 although an enzyme has been described 

 as one of its constituents which has 

 the power of converting maltose into 

 glucose. The secretion of the glands, 

 together with that of the follicles of 

 Lieberkiihn, constitutes the intestinal 

 juice. These glands are inflamed and 

 ulcerate whenever the body is burned 

 to any great extent. 



Follicles of Lieberkiihn. The folli- 

 cles or crypts of Lieberkiihn, which 

 are found throughout the entire length 

 of the small intestine, are simple tubu- 

 lar glands in the mucous membrane, 

 and not beneath it, as is the case with 

 the glands of Brunner. They are 

 lined with a layer of columnar epithe- 

 lium similar to that which covers the 

 surface of the mucous membrane and 

 the villi (Fig. 122). 



Solitary and Aominated Glands. 

 The solitary glands are found in the 

 mucous membrane of the whole small 

 intestine, in greater number, however, 



Brunner's glands (c) in the sub- in the lower part of the ileum. They 

 mucosa(s), with ducts W;mus- have a diameter of from 3 to 6 mm.. 



culans mucosse (m), and circular . 



muscular coat (/) (Schofieid). and present a round and somewhat 



prominent appearance. They are 



composed of lymphoid tissue, and contain many lymph-corpuscles. 

 They have no duct, and their product probably oozes through 

 the walls of the glands and contributes something to the in- 

 testinal juice. When these glands are aggregated they form 

 patches, and are called agminated glands or Peyer's patches 

 (Fig. 123). 



These are about twenty-five in number, though in youth as 

 many as forty-five have been seen, while in old age they are absent. 

 They occur principally in the ileum, though they are also found in 

 the lower part of the jejunum, where they are much smaller and 

 circular, and sometimes in the lower part of the duodenum. These 

 patches vary in length from 1.5 cm. to 10 cm., and in width 

 from 4 cm. to 5 cm. Like the solitary glands, they are with- 



FIG. 121. Vertical section of 

 duodenum, showing villi (a) ; 

 crypts of Lieberkiihn (6), and 



