184 ANIMAL BIOLOGY. [Parti. 



peptones, which are not only very soluble, but very readily 

 diffuse through such a moist membrane as lines the stomach and 

 intestinal canal. The process is one of anabolism or building up 

 of more .complex molecules out of less complex, and in the course 

 of the conversion of proteid into peptone there are probably 

 several mesostates, quite possibly of both orders, katastates and 

 anastates. That is to say, the original proteid molecules may 

 very possibly be first broken down into less and less complex 

 molecules, and then built up anew into more and more complex 

 molecules. 



Of the constituents of gastric juice the hydrochloric acid is 

 probably secreted by the parietal cells of the cardiac glands, 

 which are said to select sodium phosphate and sodium chloride 

 from the blood by the interaction of which the HC1 results. 

 It is questionable, however, whether the change is so simple as 

 this, and, in any case, the reaction is brought about by the 

 inherent vitality of the cells. The pepsin is probably the pro- 

 duct of katabolism (with pepsinogen, mother of pepsin, as a 

 katastate) in the lining cells of both cardiac and pyloric glands. 



The product of the small intestinal glands is termed succus 

 entericus, which is said to be a yellowish alkaline fluid. It is 

 also said that the secretion of Brunner's glands converts proteids 

 into peptones, and that of Lieberkuhn's glands is said, like 

 pancreatic juice, to act upon all the constituents of food. 



The product of the pancreas is called pancreatic juice, a colour- 

 less, transparent, viscid, and alkaline fluid. A pancreatic extract 

 may be made by soaking the gland in water, mincing, and treat- 

 ing with glycerine. The strained extract should be mixed with 

 ten to twenty volumes of a dilute (1*5 per cent.) solution of sodium 

 carbonate and filtered. Such artificial pancreatic juice, best 

 prepared from the pancreas of an animal killed soon after a meal, 

 will be found (1) to act on starch in a similar way to saliva, 

 converting it into sugar. This it does by means of a ferment 

 similar to, or indistinguishable from, ptyalin. The extract 

 will also be found (2) to act on proteids in a similar way to 

 gastric juice, converting them into peptones, or even altering 

 them still further. This it does through the special ferment 



