190 PHYSIOLOGY. 



suppose to take place, and is begun in the stomach, but is not 

 completed there ; for we observe that the long retention of the 

 alimentary matters in the stomach, whether from the insolubility 

 of the matter, or from an obstruction of the pylorus, produces a 

 greater degree of acidity ; and, in general, the acidity which 

 commonly prevails in the stomach does not disappear but in 

 the after-course of the aliment. 



CCXXXVIII. It is especially the bile, added to the mat- 

 ters which have passed from the stomach into the duodenum, 

 that is fitted to cover the acidity which appeared in the stomach. 

 It is probable, also, that the pancreatic and intestinal liquors 

 contribute to the same effect ; and it is perhaps for the same 

 purpose that the lymph is constantly added to the chyle in its 

 course. But, after all, we must rest in the general idea, and 

 own that we do not know exactly how this matter proceeds, nor 

 what the several fluids, added to the aliment in the different 

 parts of its course, truly contribute to the changes of it. 



CCXXXIX. It is probable however, that, by the mixture 

 mentioned, the peculiar fluid which we name the chyle is pro- 

 duced ; for, though it is certain that a variety of fluid matters 

 may enter the lacteals, and accompany the chyle there, it is still 

 probable that there is a peculiar fluid produced by the actions 

 of the stomach and intestines, and such as becomes the princi- 

 pal ingredient in the animal fluids afterwards formed, that is 

 strictly entitled to that appellation. This chyle does not ap- 

 pear in the stomach, but first in the duodenum, and more co- 

 piously still in the jejunum and first part of the ileum. It ap- 

 pears indeed in the whole of the ileum, coecum, and colon, but 

 in the last less copiously ; all which shows that a particular 

 mixture is necessary to it, and, at the same time, that it is not 

 made at once, but successively in the course of the intestines. 



CCXL. It remains to speak of the mixture of the oily with 

 the watery parts of the aliment. This we cannot well explain ; 

 but it is of consequence to observe here, that such a mixture is 

 actually made. It is evident that a large quantity of oil, in a 

 separate state, is taken in as a part of our aliment, but at the 

 same time no oil commonly appears in a separate state in the 

 mass of blood ; it must therefore be united with the other parts 

 of the mass in the way of mixture. Hitherto, the physiologists 



