3+6 THE POPULAR SCIENCE MONTHLY. 



istic property is that of converting starch into grape-sugar." * Ac- 

 cording to Wundt, " the mouth secretions possess, besides mechanical, 

 chiefly a chemical action the changing over of the starch and glyco- 

 gen contained in the food into sugar. The ferment body, which pro- 

 duces this transformation, ptyaline, is not a specific element of the 

 mouth-secretion, since, aside from the intestinal secretions, all tissues 

 and fluids of the body contain starch-ferment." f 



From this it will be seen that no digestive action on meat or animal 

 food takes place before reaching the stomach, and that, for vegetable 

 food even, the action of the mouth-secretions is far from all -important. 



As to the mechanical action of the mouth in preparing the food for 

 deglutition, this is not specially necessary for morsels of meat of the 

 ordinary size introduced into the mouth, while for a large portion of 

 the vegetable or plant products eaten and it is upon these that the 

 saliva exerts its chemical action mastication is necessary before they 

 can be swallowed. The meat-foods are in themselves sufficiently 

 moist, while many dried fruits, breads, and the like, in endless variety, 

 first need thorough reduction. 



A piece of jelly the size of a walnut would give little trouble in 

 swallowing, since it is moist and of a yielding character, while few can 

 swallow a pill the size of a pea without distress. Teeth and chewing, 

 then, have their purpose, but, with the exception of the incisors occa- 

 sionally, that purpose does not include meat unless it has become 

 dried ; this is with respect to the food before it reaches the stomach, 

 but, of course, the question then arises, Would it not be in a better 

 condition for digestion if it had been thoroughly masticated ? 



The food on reaching the stomach is kept in rotary motion by the 

 muscular walls, and only after a time does it begin to pass the pyloric 

 orifice, and then only by degrees, since the digestion farther on is a much 

 finer operation, and can go on but slowly. The length of time that the 

 digestion properly takes, is, according to the present knowledge of the 

 subject, several hours in fact, somewhat longer than has generally 

 been supposed. Now, if the meat is swallowed fine cut, it begins to 

 pass through very quickly, and before it has been fully acted upon by 

 the gastric juice. This action as regards meats consists in "dissolving 

 the sarcolemma from the muscular fibers, and in dissolving proteid 

 matters and converting them into peptones. . . . On starch, gastric 

 juice has />er se no effect whatever. . . . On grape-sugar and cane-sugar 

 healthy gastric juice has no effect." In fats alone it has a slight emul- 

 sifying effect, but if still in the tissue it is dissolved out. Milk is 

 accordingly acted on by being first curdled on reaching the stomach, 

 after which it is leisurely dissolved again in the desired form. 



The rotary movement of the contents of the stomach is to facili- 

 tate the action of the gastric juice to bring the various particles and 



* " Text-book of Philosophy," M. Foster, 1877. 



f " Lehrbueh der Physiologie des Menschen," W. Wundt, vierte Auflage, 1878. 



