282 PHYSIOLOGY. 



es out of the stomach into the duodenum, and it generally 

 stays in the stomach until it has undergone this change. 

 Indigestible substances have thus been vomited up, more 

 than a week after they were swallowed. All fluids which 

 are swallowed, are supposed to be taken up by absorption. 



22. If the par-vagum, or nerve which goes from the brain 

 to the stomach, be divided, digestion is impaired or suspend. 

 ed. The same happens under the influence of mental emo- 

 tions, such as grief, anger, &c. Some physiologists have 

 thought that this nerve presides over the secretion of the 

 gastric juice ; others, that it stimulates the muscular motions 

 of the stomach ; while a third class consider it to be the 

 seat of sensation in the stomach, giving rise to hunger and 

 thirst. But it is not yet fully settled what particular influ- 

 ence this nerve exerts over digestion. 



23. The chyme, on passing from the stomach, is received 

 into the duodenum. This, like the stomach, has a serous, 

 muscular, and mucous coat, and has a mucous, as well as se- 

 rous, secretion. In this portion of intestine, the chyme in 

 its passage meets with the pancreatic and the biliary fluids ; 

 the irritating properties of the acid chyme, cause these 

 fluids to be poured out in great abundance, as well as the 

 other secretions ; and these are thoroughly mixed with 

 the chyme by the contraction of the intestine. It now be- 

 comes of a yellowish, instead of a gray colour ; its acid 

 properties disappear, and large quantities of albumen are 

 developed. This is supposed, by some, to be derived from 

 the pancreatic fluid, which contains a large proportion of it. 



24. As it becomes intimately mixed with the biliary and 

 pancreatic secretions, the substance called chyle is produced. 

 Though some say it is not to be found in the duodenum but 

 only the elements out of which it is formed. But albumen, 

 which is the basis of chyle, exists abundantly in the duode 

 num ; and so also do particles of fibrin. By the microscope, 

 globules also may be detected in the chyme, similar to those 

 which are found in the chyle. 



