156 IS STARCH DIGESTED IN THE STOMACH? [BOOK II. 



The statements of various authors concerning the influence, of 

 an acid reaction upon the amylolytic action of the salivary ferment 

 differ remarkably. Thus Briicke asserts that in a solution con- 

 taining O5 of HC1 per 1000, the conversion of starch into sugar goes 

 on, whilst when the quantity reaches 1 per 1000, no action on starch 

 occurs 1 . Hammarsten found that the diastatic action ceased when 

 the quantity 2 of hydrochloric acid amounted to from 0'05 0'25 per 

 cent. Langley 3 observed that when saliva is digested with HC1 of 

 from 0*2 to 0'04 per cent, for times varying from 24 to 7 hours the 

 ferment was destroyed. On the other hand, Richet 4 asserts that 

 saliva exerts a more powerful action on starch in the presence of 

 2 parts per 1000 of hydrochloric acid, than when the reaction is 

 neutral or feebly alkaline, and Defresne contends that diastatic action 

 goes on unimpeded by the gastric juice. 



In forming an opinion concerning the important question as to 

 the extent of starch digestion, and its duration in the stomach, we 

 must rely chiefly on the researches of Langley and of Chittenden, 

 although in some particulars these observers do not agree. 



In 1881 Chittenden 5 announced that the ferment of saliva was 

 destroyed on being warmed for two hours with gastric juice contain- 

 ing 0'2 per cent, of hydrochloric acid, and even that much smaller 

 percentages of acid, as 0*025 per cent., diminished the diastatic action 

 of the ferment very materially. 



Langley 3 independently pointed out, in a study on the destruc- 

 tion of ferments in the alimentary canal, that weak solutions of 

 the salivary ferment were destroyed by heating at 40 C. with 0'014 

 per cent. HC1. 



Chittenden and Griswold 5 , although finding that the salivary 

 ferment was destroyed by very small quantities of free acid, arrived 

 at the curious result that a smaller quantity of acid increased the 

 diastatic activity. The explanation of this phenomenon was given 

 by Langley, who found that neutralised saliva converts starch into 

 sugar much more actively than unneutralised saliva. 



When therefore starch mixed with saliva enters the stomach, 

 the diastatic action will proceed, and up to a certain point may go 

 on more rapidly than with saliva which has riot been neutralised. 

 As the acid reaction becomes strongly developed the action will, how- 

 ever, rapidly slow and be arrested. 



1 Briicke, Vorlesungen, p. 280. 



2 Hammarsten, ' Einwirkung von Speichel auf Starke. ' Maly's Jahresbericht, Vol. 

 i. p. 187. 



3 Langley, ' On the Destruction of Ferments in the Alimentary Canal.' Journal 

 of Physiology, Vol. in. (1882), p. 246. 



4 Bichet, ' Du Sue Gastrique.' Journ. de VAnat. et de la Physiologie, Vol. xiv. 

 <1878), p. 285. 



5 Chittenden and Griswold, Amer. Chem. Journ., Vol. in. p. 303. See Chittenden 

 and Smith, ' The diastatic action of Saliva, as modified by various conditions, studied 

 quantitatively.' Studies from the Lab. of Phys. Chem. of Yale College, for the year 

 188485. New Haven, 1885, p. 1, et seq. 



