498 SiLBERBERG : STIMULATION OF STORAGE TISSUES 



the exact concentration of zinc sulphate which reaches the cell. 

 In this method, however, the critical or optimum point of con- 

 centration for this tissue is the twelfth and fourteenth normal. 



Part II 



In the second part of the work, the object was to determine the 

 effect of the zinc sulphate stimulation upon the respiration of the 

 storage tissue. Since the results with the potato in the foregoing 

 experiments were the most nearly constant, it was the only tissue 

 used in these latter experiments. The pieces were prepared in 

 exactly the same manner as those used in Part I. They were then 

 put into flasks which had been previously prepared in the follow- 

 ing manner : The flask was weighed, then filled with distilled water, 

 and weighed again. The first weight was subtracted from the 

 second, the remainder being the number of grams of water the 

 flask contained, or the volume of the flask in cubic centimeters 

 (i gm. H^O = I C.C.). The three flasks used were always labeled 

 I., II., and III. The volume of flask L was 94.093 c.c; the 

 volume of flask II., 90.506 c.c.,and that of flask III., 105.433 c.c. 

 Flask I. was always used for the control. Before using, the 

 flasks wxre always thoroughly washed in tap w^ater, then rinsed 

 three times in distilled water, and allowed to dry over night in an 

 inverted position. Whenever it was necessary to use them again 

 on the same day they were washed, they were dried in a drying 

 oven at 100^ C. 



In the first experiment ten pieces of potato were used ; in the 

 second, fifteen ; and in all the following experiments, twelve. After 

 the pieces had been dipped and rolled on filter paper, they were 

 put into the respective flasks, and cotton stoppers were inserted 

 in the mouths of the flasks, which were then inverted over mer- 

 cury cups (see figure i, b). 



For analyzing the gas the Bonnier-Mangin instrument for gas 

 analysis was used. In transferring the flasks from the mercury 

 cup to the Bonnier-Mangin apparatus, a moistened finger tip was 

 always held over the mouth of the flask until it was inserted in the 

 mercury cup of the gas-analyzer. Before inserting it in the cup, 

 the pieces in the f!ask were always shaken about a little to make 

 sure that the gas in the flask would be uniform in composition- 



