RELATIONS OF DIGESTION AND ABSORPTION 251 



of a meal is very closely proportionate to the quantity of food of 

 any one kind which is ingested. The following are results obtained by 

 Klugine, the "calculated" figures being estimated on the assumption 

 of strict proportionality between the volume of secretion and the mass 

 of the given type of food which was ingested. 



Quantity Quantity of gastric juice: 



of food. Observed. Calculated. 



Type of Food. grams. c.c. c.c. 



Raw meac ......*.. 400 106 99 



Raw meat . . . .- .'_.-. . 200 41 50 



Raw meat . '.....". ". 100 27 25 



Boiled meat . . . . . . . -. 200 42 42 



Boiled meat ........ 100 21 21 



Milk I...!. 600 56 53 



Milk 500 41 44 



Milk 200 17 18 



Soup of oats and meat 600 43 41 



Soup of oats and meat . . ..... 300 20 21 



Meat, bread and milk . . . . . -. 800 83 90 



Meat, bread and milk . . . . . 400 41 45 



It is evident that the calculated figures agree as closely as could be 

 desired with those actually observed. Evidently, then, there is not 

 a constant amount of gastric juice secreted for each meal, but the 

 amount furnished is proportionate, for any one kind of food, to the 

 mass ingested. As Arrhenius has pointed out, this would appear at 

 first sight to be an uneconomical arrangement, since a very small 

 quantity of a digestive enzyme is capable, in time, of digesting a 

 very great excess of foodstuff. The length of time required for diges- 

 tion, however, if the mass of enzyme available for each meal were a 

 limited, fixed quantity, would be so extremely variable that the 

 economy of the tissues could not be adjusted to so irregular a method 

 of furnishing their needs. For instance if about four and a half hours 

 are requisite for the gastric digestion of 100 grams of raw meat by a 

 given amount of pepsin then it may readily be calculated from the 

 Schiitz-Borrissov Rule, which pepsin obeys, that no less than 70 hours 

 would be requisite for the digestion of 400 grams and eighteen days 

 for the digestion of a kilogram. As a matter of fact, however, the 

 process of gastric digestion is carried out in successive portions of 

 the foodstuffs, a fresh supply of gastric juice being furnished for each 

 portion of food that comes into contact with the surface of the gastric 

 mucosa. In this way much more rapid and uniform digestion is 

 secured than would otherwise be possible. 



The hydrolysis of foodstuffs in the alimentary canal appears to 

 follow the same quantitative laws as the hydrolyses by the corre- 

 sponding enzymes in vitro. Thus Gastric Digestion follows the Schiitz- 

 Borrissov rule, while the hydrolysis of protein in the small intestine 

 by Pancreatic Juice follows the monomolecular logarithmic formula: 



log ^r~ = kt 

 which holds good for the action of this enzyme in glassware. 



