214 



ANIMAL PHYSIOLOGY. 



[LESSON 62. 



FIG. 837. 



common with the remainder of the intestinal glands, were really dis- 

 covered by Peyer, who describes them as being " as numerous as the 

 stars in the firmament of heaven." 



933. These glands lie, not in the mucous but in the sub mucous 

 tissue, where they form a continuous layer of white, flat bodies, of 

 irregular size, surrounding the whole intes- 

 tine. Each gland consists of numerous 

 minute lobules, of which the ducts (a) 

 open into the mucous membrane of the 

 intestine. A figure of these glands is 

 given (Fig. 337). 



934. The villi of the duodenum (Fig. 

 338) are usually larger and broader than 

 those of the Jejunum, and are remarkable 

 for the possession of a large vessel in the 

 centre of each villus ; throughout the small intestines, at the bases 

 of the villi, and surrounding them, are the mucus-crypts, or folli- 

 cles of Leiberkuhn. 



935. They appear like so many minute holes upon the surface of 

 the mucous membrane ; examined by dissection, they are found to be 

 long, narrow, deep tubes, or cavities, giving the idea of a villus 

 pushed into the mucous membrane, and inverted, like inverting the 

 finger of a glove. In life these glands are filled with a clear, fluid 

 secretion, called the intestinal juice. 



Brunner's glands. 



FIG. 838. 



FIG. 339. 



Villi, of human Duodenum. Jejunum, human. 



936. In the human jejunum the villi and Leiberkuhnian follicles 

 are well seen (Fig. 339) ; it will be readily perceived that, by the 

 arrangement of these follicular glands, the surface of the mucous 

 membrane is thereby greatly increased ; where there is not room for 

 another villus, there is yet room for a series of minute apertures at 

 its base. 



937. The villi of the small intestines contain in their interior 



