254: DIGESTION. 



quantity in the stomach, does not seem to be important. 

 It is usual in these experiments to separate mucus and 

 extraneous matters from, gastric juice by filtration before 

 it is used; and the digestive properties of the fluid thus 

 treated are not sensibly affected when the mucus is allowed 

 to remain. 1 



In studying the physiological action of the gastric juice, 

 it must always be borne in mind that the general process of 

 digestion is accomplished by the combined, as well as the 

 successive action of the different fluids. The act should be 

 viewed in its ensemble ', rather than as a process consisting of 

 several successive and distinct operations, in which different 

 classes of principles are dissolved by distinct fluids. The 

 food meets with the gastric juice after having become im- 

 pregnated with an immense quantity of saliva ; and it passes 

 from the stomach to be acted upon by the intestinal fluids, 

 having imbibed both saliva and gastric .juice. By studying 

 the different digestive fluids in too exclusive a manner, many 

 physiologists, while professing to assign definite and distinct 

 properties to each, thus investing the function of digestion 

 with an attraction of simplicity, have necessarily ignored or 

 distorted facts, and assumed a completeness for the sum of 

 our information on this subject, which does not exist. There 

 could be no more serious barrier than this in the way of 

 farther knowledge of a function, concerning which much 

 remains to be learned. 



"When the acts which take place in the mouth are prop- 

 erly performed, the following alimentary substances, commi- 

 nuted by the action of the teeth and thoroughly insalivated^ 

 are taken into the stomach : muscular tissue, containing the 



1 Blondlot has shown (Traite Analytique de la Digestion, Paris, 1843, p. 292), 

 that mucus is not acted upon by the gastric juice, even after prolonged contact at 

 the temperature of the body. The mucus which is secreted in the stomach is, 

 as far as has been ascertained, precisely like the secretion of ordinary mucous 

 membranes ; and it does not possess any peculiar properties, like, for example, 

 the viscid secretion from the intestinal mucous membrane. 



