.ACTION OF THE SMALL INTESTINE. 607 



and the movement is altogether in one direction ; from the stomach 

 towards the intestine. The movement by which the chyme is immedi- 

 ately sent into the duodenum, is thus effected : the longitudinal fibres, 

 which pass from the cardiac to the pyloric orifice, contract, and approxi- 

 mate the two orifices ; the pyloric portion then contracts, not so as to 

 direct the chyme into the splenic portion, but towards the duodenum : 

 in this manner, the chyme passes from the stomach : and, as fresh por- 

 tions are formed, they are successively sent onwards; the peristaltic 

 action becoming more and more marked and frequent, and extending 

 over a larger portion of the organ, as chymification approaches its ter- 

 mination. As the chyme is discharged into the small intestine, the 

 stomach gradually returns to its former dimensions and situation. 



f. Action of the Small Intestine. 



The changes in the alimentary mass in the small intestine, are not 

 less important than those already considered. They consist in a farther 

 change of the chyme into a substance, whence chyle can be extracted 

 by the action of the chyliferous vessels or lacteals. Whether chyle 

 be separated in the intestine, in a state fit for chyliferous absorption, 

 or be formed by those vessels, will have to be canvassed hereafter. In 

 common language, however, it is said to be separated there, and the 

 process, by which this is accomplished, is called chylification. 



As the chyme proceeds into the duodenum, it readily finds space, 

 until towards the end of chymification, when the intestine not unfre- 

 quently experiences considerable dilatation. The presence of the ali- 

 mentary mass augments the secretion from the mucous membrane; 

 and occasions a greater flow of the biliary and pancreatic juices. MM. 

 Leuret and Lassaigne 1 found, when they applied vinegar, diluted with 

 water, to the external surface of the small intestine in a living animal, 

 that a considerable quantity of serous fluid was immediately exhaled. 

 The same application, made to the follicles of the intestine, excited 

 the secretion of a greater quantity of mucus; and its application to 

 the mouths of the choledoch and pancreatic ducts caused the orifices 

 to dilate, and a greater discharge of bile and pancreatic juice. It is 

 in this local manner that many of the cholagogue purgatives produce 

 their effect. Calomel exerts its agency on the upper part of the intes- 

 tinal canal more especially; and the irritation it induces in the mucous 

 membrane at the mouth of the ductus communis choledochus is propa- 

 gated along the biliary ducts to the liver, the secretion of which is 

 thus augmented, but not by any specific action exerted on the organ, 

 as has been often imagined. As the chyme is acid, it induces the same 

 effects on the follicles as the acid employed in the experiments of MM. 

 Leuret and Lassaigne. 



The chyme does not remain so long in the intestine as food does in 

 the stomach. The successive arrival of fresh portions propels the first 

 onwards ; and the same effect is induced by the peristaltic action of 

 the intestines, an involuntary, muscular movement of an irregular, 

 undulatory, oscillatory or vermicular character, which consists in an 



1 Recherches sur la Digestion, Paris, 1825. 



