DIGESTIBILITY OF BREADS. 



67 



These experiments were made to ascertain the effect of variations in the time of 

 exopsure. The conditions of experiment were otherwise as in Table 3. 



It is plain that under the conditions of the experiment, the products of digestion 

 accumulating in the beakers soon became a more powerful retarding agent than the con- 

 stituents of the powders. The greatest difference in the digestibility of these breads is 

 seen at the end of one and a half hours' digestion, A'iz., 100, 84.8, 62.5 and 60. At the 

 end of three and a half hours, the bread made from the tartaric acid powder has a smaller 

 residue than the plain bread. These experiments are interesting, as they shew well how 

 difficult it is to express the relative digestibility of substances in terms of the time occu- 

 pied to complete digestion. Those who regard favourably this latter mode of experi- 

 mentation, do not always consider the fact that the products of digestion may vary with 

 the speed of digestion. Grutzner ' found that the intensity of the ferment action in the 

 case of salivary digestion determined the nature of the digestion product — a slow action 

 producing erythrodextrin from starch, while during rapid digestion, sugar was chiefly 

 formed. Now, if the products of digestion accumulating in two digestion mixtures are 

 not alike, their effects on the ferment will not be similar, and it would be manifestly 

 erroneous to compare the results without a correction of this source of error. Indeed, if 

 the digestion be prolonged, the retarding inlluence of the accumulating products may 

 become so powerful as to lead to conclusions absolutely false. In all the experiments 

 made by the author, digestion was stopped, while still active, by boiling the mixtures 

 simultaneously, thus reducing to a minimum any error arising from accumulating pro- 

 ducts of ferment action. 



The experiments detailed in Series II, Tables 1 to 5, shew the influence of these 

 baking powders on both the amylolytic and proteolytic ferments of the pancreatic fluid. To 

 study the effects on the former alone the following experiments were made : — One gramme 

 of each bread was taken with 2 c. c. of ferment made up to 50 c. c. and kept at 40' C. for 

 two hours. Digestion was stopped by boiling, and the mixture filtered, the residue well 

 washed and the dextrose in the filtrate estimated by standard Fehling's solution. The 

 resiilts were as follows : — 



Table 6. — Pancreatic Digestion (Amylolytic action). 



In these experiments the amount of reducing substance formed was for the sake of 

 convenience estimated as dextrose. This, of course, only expresses comparative results, as 

 dextrose is but the final product of the change. Between dextrin, which has no reducing 

 power, and dextrose, there are other bodies, notably maltose, formed in much larger quan- 

 tities, the latter has a reducing power of but 66 (dextrose 100), while a.chroodextrin 

 and other intermediate products have very slight reducing action. The total reducing 



' Phluger's Archiv der Physiologie, xii. 297. 



