ALIMENTARY CANAL IN THE BEE 535 



to the quantity ol' glycerine or the concentration of the sugar 

 sohition, as we added to 50 c.c. of the latter an amount of 

 extracts varying between 0-1 and 25 c.c. In order to ascertain 

 the real cause of this phenomenon, we conducted special 

 experiments on the following plan. Extracts were prepared 

 simultaneously from the stomachs of bees of equal concentra- 

 tion in water and in a mixture of equal parts of glycerine and 

 water. To 25 c.c. of 10 per cent, sugar solution was added 

 a certain amount of extract (see Table VII), and the mixture 

 resulting made to reach 50 c.c. by addition of a corresponding 

 amount of water or its mixture with glycerine. As a result, 

 in all the tests analysed, the concentration of cane-sugar 

 reached the same level, differing from each other only in 

 the quantitative content of ferment. Thus we have con- 

 ducted two parallel series of experiments in water and in 

 a mixture of water and glycerine ; the tests of one series of 

 experiments differed from the other only in the presence of 

 glycerine in, it. The results obtained are given in Table VII. 



On comparing the results of analyses adduced in Table VII 

 we can state without doubt that in extracts of glycerine with 

 water inversion increases only to 10 per cent, of the content of 

 glycerine estimated in relation to the total volume of the 

 liquid analysed. On further addition of glycerine the activity 

 of invertase falls perceptibly. In parallel experiments with 

 pure water extracts the degree of inversion rises according 

 to the increase in the quantity of extract, that is to say, of 

 invertase. 



Thus, in certain quantities, glycerine has a repressive influ- 

 ence on the invertase as represented in Curve 3. 



In order to determine the influence of the solvent upon the 

 activity of invertase extracts from the stomachs of fifteen bees 

 per 15 c.c. of water, 15 c.c. of glycerine, and, lastly, per 15 c.c. 

 of physiological solution of common salt, were prepared in 

 similar conditions ; to each extract were added 5 drops of 

 toluol for conserving purposes. On the following day to 

 50 c.c. of 5 per cent, solution of saccharose were added 5 c.c. 

 of the extracts named and 10 drops of toluol ; after twenty- 



