APPENDIX. 337 



One molecule of gelatinous starch is converted into n molecules of 

 soluble starch. 



One molecule of soluble starch = 10 (C 13 H ?0 10 )-f 8 (H 2 0) 

 = 1 Erythro-dextrin (giving red with iodide) Maltose. 



9 (C lf H 30 10 ) + (C 12 H 22 O n ) 



= 2. Erythro-dextrin (giving yellow with iodine) Maltose. 



8i r\ TT /i \ | k) / r\ 'TT r\ \ 



I v^ 1Q l Q0 v>' ) ] \/ (\u ij-o vy ) 



= 3. Achroo-dextrin Maltose. 



7 (0,, H JO 10 ) + 3 (0,, H M OJ 



And so on; the resultant being: 



10 (0,, H !0 O,.) + 8 (H, 0) = 8 (0,. H M ) + 2 (0,, H 20 10 ) 



Soluble starch Water Maltose Achroo-dextrin. 



Pancreatic juice and intestinal juice are able to turn the achroo-dex- 

 trin which remains into maltose, and maltose into glucose (dextrose). 

 It is doubtful whether saliva possesses the same power. 



(2.) Proteolytic convert proteids into peptones. The nature of their 

 action is probably hydrolytic. The proteolytic ferments of the body are 

 called Pepsin, acting in an acid medium from the gastric juice. Trypsin, 

 acting in an alkaline medium from the pancreatic juice. The Succus 

 entericus is said to contain a third such ferment. 



(3.) Inversive, which convert cane sugar or saccharose into grape 

 sugar or glucose. Such a ferment was found by Claude Bernard in the 

 Succus entericus; and probably exists also in the stomach mucus. 



2 C ia H 22 O n + 2 H 2 = C 12 H 24 12 + C 12 H 24 13 

 Saccharose Water Dextrose Laevulose. 



(4.) Ferments which act upon fats; such a body called Steapsin has 

 been found in pancreatic juice. 



The ferments Amylopsin, Trypsin, and Steapsin, are said to exist 

 separately in pancreatic juice, and if so, make up what was formerly called 

 Pancreatin and which was said to have the functions of the three. 



(5.) Milk-curdling ferments. It has been long known that rennet, a 

 decoction of the fourth stomach of a calf, in brine, possessed the power of 

 curdling milk. This power does not depend upon the acidity of the gas- 

 tric juice, since the curdling will take place in a neutral or alkaline 

 medium; neither does it depend upon the pepsin, as pure pepsin scarcely 

 curdles milk at all, and the rennet which rapidly curdles milk has a very 

 feeble proteolytic action. From this and other evidence it is believed 

 that a distinct milk-curdling ferment exists in the stomach. W. Roberts 

 has shown that a similar but distinct ferment exists in pancreatic extract, 

 which acts best in an alkaline medium, next best in an acid medium, 

 and worst in a neutral medium. The ferment of rennet acts best in an 

 acid medium, and worst in an alkaline, the reaction ceasing if the alka- 

 linity be more than slight. 

 VOL. II. 22. 



