138 ORGANS OP DIGESTION. 



The Glands of Brunner. These glands may be studied 

 in thin vertical sections of the duodenum of the cat or dog. 

 They lie in the submucosa, and consist of branched tubes, 

 which are much convoluted and are lined throughout with 

 cylindrical epithelium. Towards the muscularis externa they 

 are invested by a special layer of unstriped muscular fibres, 

 originating from the muscularis mucosae. The ducts of these 

 glands, after penetrating the muscularis mucosze, diminish in 

 calibre as they pass outwards towards the surface between the 

 Lieberkuhn's tubes. The epithelium with which they are lined 

 exhibits a striking contrast to that of the tubes, the elements 

 being slenderer and much more readily stained with carmine. 



Peyer's Follicles. The best preparations are to be ob- 

 tained from the lower end of the ileum of the dog or cat. The 

 intestine of the rabbit may also be used. Thin sections of 

 these parts may be prepared as above directed, with the excep- 

 tion that the time occupied in each stage of the process of 

 hardening may be shortened. The hardened portions must, 

 moreover, be embedded in wax-mass rather than in gum. The 

 sections, whether stained or not, should be steeped for twenty- 

 four hours in water, and then shaken in the manner recom- 

 mended for the preparation of sections of the lymphatic 

 glands. They are finally mounted in glycerin. In this way 

 the recticular tissue both of the mucosa and of the follicle is 

 well shown. From sections of Peyer's patches, prepared in 

 the manner previously described, we learn that each follicle is 

 surrounded by a large lymphatic sinus that each is deeply 

 embedded in the submucosa, sometimes approaching the mus- 

 cularis externa that a small part of each penetrates the mus- 

 cula?'is mucosae and projects into the mucosa, some of the 

 summits losing themselves in its tissue without any defined 

 limit, others reaching up to the epithelium. When this is the 

 case, the epithelial elements are smaller, and consist of several 

 layers of polyhedral cells. Both in situations where there are 

 distinct patches, and in those regions in which (as occurs in the 

 ileum of the cat and dog) the whole of the submucosa is occu- 

 pied with follicles, the individual follicles are in continuity at 

 their widest part. The network of lymphatic vessels of the 

 submucosa, with which the sinuses of the follicles, as well as 

 the tymphatics of the villi, are in immediate communication, 

 can be readily filled with soluble Prussian blue, by the method 

 of puncture. It is most easity accomplished in large rabbits. 

 Half per cent, silver solution may be also used for the demon- 

 stration of the endothelial lining which all these vessels pos- 

 sess. 



To prove that in the absorption of fat the network of the 

 stroma of the villi is concerned, a rat, hedgehog, or kitten is 

 allowed to remain without food for a day or two, and then fed 



