THE DIGESTIVE TRACT. 603 



described " ampullae " in the villi, which, by some physiologists, 

 were considered to be widenings of the chylif erous vessel at the 

 base of the villus. I have made the presence of such openings cer- 

 tainly probable, even though positive proofs of their existence are 

 still wanting. 



Along the epithelial investment of the villi goblet-like forma- 

 tions are often seen, more numerous in animals having an in- 

 creased mucous discharge from the intestine i. e., diarrhoea. In 

 1868 I maintained that these formations were the shells of cement- 

 substance, after the contents the mucus had been emptied 

 out. This theory was contrary to the ideas of some observers, who 

 claimed that the goblets had been artificially produced, or were 

 specific secretory organs. Bonders and Kolliker had, previously 

 to the publication of my views, described these formations as con- 

 nected with the secretion of mucus, and this idea proved to be 

 correct. 



The epithelial, investment of the mucosa of the intestine forms 

 tubular glands, the intestinal glands or so-called crypts of Lieber- 

 Mhn, which are located beneath the level of the mucosa, and, 

 being more numerous than the villi, empty by minute openings 

 around the base of the villus. Their lining epithelium is col- 

 umnar, exhibiting the same basal seams as those covering the 

 villi. The intestinal glands are absent in localities where lymph- 

 follicles are imbedded in the mucosa. 



The mucosa of the duodenum, chiefly in its upper third, holds 

 racemose glands, which are situated below the level of the lower 

 extremities of the intestinal glands ; these are called Brunner's 

 glands, and their secretion is considered to be mucus. In the 

 descending portion of the duodenum they gradually become 

 scantier, and especially so below the openings of the bile-duct. 



The mucosa of the small intestine is supplied with a double 

 layer of smooth muscle-fibers, independent of the muscle-layers of 

 the intestine itself. The innermost is circular, running between 

 the tubules and penetrating through vertical prolongations the 

 myxomatous structure of the villi, where several delicate bundles 

 are formed by it ; the outer muscle-layer is longitudinal, being 

 in most localities decidedly broader than the circular layer. 

 Transverse sections of portions of the small intestines, hardened 

 by having been placed in a solution of chromic acid immediately 

 after .the animal's death, plainly show that where the muscle of 

 the intestine is broad, consequently contracted, and the caliber 

 of the intestine narrow, the villi are elongated and thread-like or 



