A HISTORY OF SCIENCE 



stomach namely, the pancreas has a share in diges- 

 tion, and in the course of the ensuing decade it came to 

 be known, through the efforts of Eberle, Valentin, and 

 Claude Bernard, that this organ is all-important in 

 the digestion of starchy and fatty foods. It was found, 

 too, that the liver and the intestinal glands have each 

 an important share in the work of preparing foods for 

 absorption, as also has the saliva that, in short, a 

 coalition of forces is necessary for the digestion of all 

 ordinary foods taken into the stomach. 



And the chemists soon discovered that in each one 

 of the essential digestive juices there is at least one sub- 

 stance having certain resemblances to pepsin, though 

 acting on different kinds of food. The point of resem- 

 blance between all these essential digestive agents is 

 that each has the remarkable property of acting on 

 relatively enormous quantities of the substance which 

 it can digest without itself being destroyed or apparent- 

 ly even altered. In virtue of this strange property, 

 pepsin and the allied substances were spoken of as fer- 

 ments, but more recently it is customary to distinguish 

 them from such organized ferments as yeast by desig- 

 nating them enzymes. The isolation of these enzymes, 

 and an appreciation of their mode of action, mark a 

 long step towards the solution of the riddle of diges- 

 tion, but it must be added that we are still quite in the 

 dark as to the real ultimate nature of their strange 

 activity. 



In a comprehensive view, the digestive organs, taken 

 as a whole, are a gateway between the outside world 

 and the more intimate cells of the organism. Another 

 equally important gateway is furnished by the lungs, 



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