264 RESPIRATION, FERMENTATION AND DIGESTION 



such as lamp chimneys in such manner that the rubbers form 

 the bottoms of the cylinders.. Fill one with water and the other 

 with solution for fermentation. Note results hourly. 



334. Products of the Fermentation of Sugar. Make 1,000 g. 

 of Pasteur's solution by adding to 838 cc. of water, 150 cc. of 

 grape-sugar, 10 cc. ammonium tartrate, 2 g. each of magnesium 

 sulphate, calcium phosphate, and 2 g. of potassium phosphate. 

 Pour 250 cc. of the solution in a glass cylinder and add 5 g. com- 

 pressed yeast and keep at a temperature of about 25° C. Cover 

 the vessel with a glass plate, or fit with a cork stopper. Test the 

 air above the liquid for carbon dioxide a few hours later. Place 

 some of the solution in a distilling apparatus and test the con- 

 densation for alcohol. Make a strong solution of potassium 

 bichromate in water, and add a few drops of sulphuric acid. 

 Pour a few drops of this mixture into a test-tube containing some 

 of the distillate. The presence of alcohol will be denoted by the 

 appearance of a greenish color. The fermentation tested above 

 is produced by an enzyme excreted by the yeast cells. Tests of 

 the effects of anaesthetics may be made. 1 



335. Digestion. Digestion in plants includes the processes by 

 which certain insoluble and non-dialyzable substances are con- 

 verted into diffusible form, and other material is changed in such 

 manner that it may be absorbed and used by protoplasm. These 

 changes embrace hydrolyzation, and oxidation and splitting up 

 of the various food substances. Digestion of some substances 

 may be carried on by the direct action of protoplasm, or may be 

 effected by the catalytic action of certain proteid secretions 

 termed enzymes. All enzymatic effects are not productive of 

 plastic or diffusive material, and hence are not to be included in 

 digestion. A number of these enzymes have been isolated and 



1 Bokomy, Th. Empfindlichkeit einiger Hefenzyme gegen Protoplasmagifte. 

 Wettendorfers Zeitschrift f. Spiritus-Industrie. September, 1900. 



For a comprehensive account of fermentations by minute organisms- see Duclaux, 

 E. Traite de Microbiologie, 2 : 1899, and 3 : 1900. 



Jorgensen, A. Micro-organisms and fermentation. Trans. Miller & Leunholm. 

 3d Ed. 1900. 



