In addition to Lieberkulin's follicle. or tubes, NVIlteh exist in the whole of the ,maller there ak te other glandular or secreting structures, imbedded in the t•certa ill per Lions of intestinal tract. which require shlerat ion. Those are : ( I 1 Itrunner's ((IA% . IabIt.tI occur only in the duodenum; (2) solitary which semi to occur in all parts of the intestines, Loth small. and large; and Of l'eyer's glands, which n re usu ally confined to the ileum.
Iframo gfuntis are most abundant at the pyloric• end of the duodenum. In struc ture they resemble the jinn cures. their ultimate elements being bunches of vesicles. from which minute duets arise, xvhielt coalesce and form hrger duets., through which the secretion is poured into the duodenum. It is believed that they secrete a fluid simi lar to the pancreatic juice. The solitary glands occur in all parts of the intestine. but nee perhaps, more numerous in the jejunum than elsewhere. Each gland is a simple mem branous thisk-shajled vesicle. the neck correspond ing to the surface of the intestine, while the rounded base lies in the sulanticous tissue. The neck presents no ollening, and how the contents, which of nuclei and granular partieles, are discharged into the intestine is not clearly known. _1s WT. never see them larger than a mustard-seed, Nye may presume that on Mt:tinily.; that size they burst. Prtrt r's glunds are :111p:trendy inert. aggregations of solitary glands, forming oval patches in the patches vary in size and number. being largest toward the estrum, where their long diameter sometimes measures three or four inches, and smallest toward the jejunum. where their her varies from fifti•eff to twenty, or even more. Nothing certain is known regarding the uses of these solitary or aggregated glands; lint as they largest during the digestive provers• WV roust infer that they are in some way connected with that function. Possibly the peeuliar odor of the farces may be due to their secretion. In typhoid or enteric fever, and in phthisis, these glands become ulcerated, which probably occa sions the diarrlma so common in these diseases.
Brunner's glands are much more developed in the herbivora than in the earnivora Peyer's, on the other hand, are most developed in the latter.
We have endeavored. in the preceding sen tences, to give the reader some idea of the com plicated struetlire of the mucous and subnincous coat of the small intestines; we now proceed to notice the chief uses of the muscular coat of the intestine. This coat, as has been already men tioned, consists of two layers of muscular fibres —namely. circular and longitudinal fibres, of which the former lie next to the subnmeous coat. The peristaltic or vermicular action, by which the substanees whieh enter the duodentun from the stomaeh are moved onward, is due to this muscular coat. A person who has once seen the abdomen of an aninml laid open immediately after death will have a better idea of the nature of this movement than can be afforded by any description. It commences about the pyloric
third of the stomach, whence successive wave like movements are propagated through the entire length of the intestinal canal. It is the rapid succession of these alternate contractions and relaxations that impels the intestinal eon tents onward. and occasions those movements which, front their resemblance to the writhings of a worm, have been termed vermicular. It is very probable that the rapidity of this movement varies in different individuals—those persons, for example, whose bowels act twice daily hay ing a more rapid vermicular motion than those in whom the net of defecation occurs only once in the twenty-four hours.
We have now to consider the effects produced on the chyme by the different fluids with which it becomes mixed in the small intestine. These fluids are: (I) The bile: (2) the pancreatic juice: and (3) the intestinal juice.
The bile (q.v.) is a faintly alkaline or neutral fluid containing two essential constituents, one of which is of a resinous nature, while the other is a pigment. The resinous constituent is not pre cisely identical in all kinds of bile. but it gen erally consists of a soda salt whose acid is either glycocholic or taurocholie acid, or of a mixture of these salts. Streeker. to whom we are mainly indebted for our knowledge of the chemistry of the bile. states that in most mammals the resin ous constituent merely differs in the varying proportions in \Odell the tanrocholates and gly cocholates are intermixed. the former usually preponderating. Aecording to Lehmann, the resinous constituent amounts to at least 75 per cent. of the solid residue. The bile pigment oc curs in the bile of different animals under two forms—namely. as a brown and as a green pig ment, the latter probably only differing from the former in being more 'Uglify There has never been a ease in which physiologists have had an opportunity of directly observing the quantity of bile that is secreted by the human subject, and all our information on this subject is derived from observations on animals in which the common bile-duet (see LtvEn) has been tied and a fistulous opening established into the gall bladder. if the same proportion of bile to bodily weight holds good in man as in the dog. a man weighing 1 in pounds would secrete daily about five pounds of bile. All observers agree that the :Amount of the biliary secretion varies directly with the quantity of food: and as animals with hiliary fistula( (in whom all the bile escapes externally, instead of making its way into the duodenum) usually have voracious appetites, experiments on this point are easily made. There is great discrepancy of opinion as to how soon after a Inca] the bile flows most abundantly into the intestine. According to Kiilliker and whose experiments were made on dogs fed only once a day. very little bile is secreted in the first and second hour after a meal, more in the third, fourth. and fifth, the maximum being sometimes attained in the fifth, sometimes not till the eighth hour.