1911.] Decomposition of Organic Compounds. 263 



when making the connections, and the difference of potential to be described 

 could in no degree be attributed to friction inside the cell. 



In every case the cells when set up were allowed to settle down and were 

 tested before the commencement of any experiment. After these precautions 

 against experimental error, the way seemed clear for a study of the actual 

 effect produced by the vital activity of living organisms. 



The fermentative activity of yeast upon solutions of sugar seemed to offer a 

 promising subject for investigation, and ordinary commercial yeast in a very 

 fresh condition, with glucose as a medium, was employed, because of the 

 rapid and marked fermentation which is developed, and which one might 

 expect to be reflected in a pronounced electrical effect. 



Tor the study of the fermentation of yeast a very useful form of diaphragm 

 can be constructed from parchment dialysing tubes, cut into convenient 

 lengths. A glass cup tied firmly at one extremity and a glass ring at the 

 other served to keep it distended, and as the tube could be discarded after 

 each experiment, this kind of porous cylinder proved very convenient and 

 was used in preference to a porous pot. The relative size of the cylinder and 

 glass jar was such that when each contained 100 c.c. the level of the outer 

 and inner fluids was approximately the same. 



As an arbitrary standard it was found convenient to take 50 grm. of yeast 

 and mix with 100 c.c. of water and to apportion 10 c.c. of this for each cell. 

 By this method approximately the same quantity of yeast would be used for 

 each cell, and the results of experiments would be comparable one with 

 another. 



The cell being set up, 100 c.c. of a given solution of glucose was poured 

 into the cylinder and into the jar, the electrodes were inserted and the 

 necessary connections made, and readings taken on the galvanometer deter- 

 mined the constant relative charge on the electrodes. 



The yeast could now be introduced into the outer fluid, and after this was 

 done readings of the galvanometer were taken at frequent intervals. Tor a 

 short time after the introduction of the yeast no E.M.F. could be observed, 

 but as the organism commenced its activity and the fermentation was set up, 

 a gradually increasing voltage was registered, the rise of the voltage being 

 determined by the concentration of the glucose solution, the temperature, and 

 the quantity of yeast added. 



On disconnecting the yeast-glucose cell, and substituting for it a standard 

 cell, it was always found from the swing of the galvanometer that the glucose 

 solution with yeast acted as the zinc of an ordinary galvanic cell, the current 

 passing in the cell from the yeast-glucose solution to the glucose solution. 

 Moreover, when the inner fluid was inoculated instead of the outer fluid, the 



VOL. LXXXIV. — B. X 



