414 THE ENZYMES OF THE INTESTINAL JUICE. [BOOK II. 



seem to indicate that the diastatic activity of the intestinal juice 

 secreted in the upper part of the small intestine is very much 

 greater than that of the juice secreted by the ileum. That this 

 activity may play no unimportant part in the intestinal digestion of 

 some animals is rendered probable by an experiment of Rb'hmann's, 

 in which 50 c c. of a 2 / starch mucilage were absorbed by a 

 segment of jejunum 20 centim. long in the course of one hour 1 , it 

 being probable that the process of absorption presupposes an antece- 

 dent diastatic conversion of starch into sugar. 



Brown and Heron have shewn that under the influence of the 

 diastatic ferment of the intestine, starch is converted into maltose, 

 the latter sugar being, however, rapidly converted into dextrose 

 through the agency of another enzyme. Their experiments led them 

 to the opinion that the mucous membrane of the ileum is richer in 

 diastatic ferment than that of the duodenum or jejunum, and in this 

 respect they do not agree with the direct observations of Rohmann 

 on dogs with Vella-fistulse. 



Action of the I* 1 tne vear 1871, Paschutin 2 , for the first time, 

 intestinal juice drew attention to the fact that the intestinal mucous 

 on cane sugar, membrane, in its whole extent from the pylorus to the 

 The "intestinal iii _ co ii c valve, contains a ferment which converts cane- 

 inverting en- . . ^ TT1 . 1-11 

 zyme > sugar into grape-sugar. When cane-sugar is boiled 



with dilute mineral acids, or subjected to the action 

 of so-called inverting ferments (of which one exists in yeast), it is 

 readily split up into a molecule of dextrose and a molecule of levu- 

 lose, thus : 



(^A, + H 2 o = p,^ + cy^o.. 



Saccharose. Dextrose. Levulose. 



To the process the term inversion is applied, and to the mixed 

 sugar which results from it the name of invert-sugar. 



The researches of Rohmann 3 , Bastianelli 4 , and particularly of 

 Brown and Heron 5 , have demonstrated in the fullest manner the 

 accuracy of Paschutin's discovery that an inverting enzyme is con- 

 tained in the intestinal mucous membrane and in the intestinal 

 juice. There is, however, a consensus of opinion on the part of those 



1 Bohmann, op. cit. p. 429. 



2 Dr V. Paschutin, ' Einige Versuche mit Fermenten, welche Starke und Eohrzucker 

 in Traubenzucker verwandeln,' Archiv f. Anat. u. Physiol. 1871, pp. 305 384. Refer 

 specially to p. 374. The merit of this very important discovery has been erroneously 

 attributed by many writers to Claude Bernard. Thus Bohmann says, " Auf die 

 iuvertierenden Eigenschaften des aus Thiry'schen Fisteln gewonnenen Darmsaftes hat 

 zuerst Cl. Bernard aufmerksam gemacht." " J'ai decouvert qu'il possede une action 

 inversive tres puissante sur le sucre de canne." Bernard, Lemons sur le Diabete, Paris, 

 1887, p. 259. 



3 Bohmann, op. cit. p. 432. 



4 C. Bastianelli, 'Ueber die physiologische Bedeutung des Darmsaftes.' Abstracted 

 from the original paper in the Bollet. d. R. Accad. med. di Roma, Vol. xiv. pp. 140 180, 

 in Jahresb. f. phys. Chem. 1889, p. 238. 



5 Horace T. Brown and John Heron, ' Die hydrolytischen "Wirkungen des Pankreas 

 und des Diinndarms,' Annalen d. Chemie u. Pharmacie, Vol. cciv. (1880), pp. 228 251. 



