72 
Proceedings of Royal Society of Edinburgh. [sess. 
the ordinary temperature of the room, the evaporation occurring 
in a large bell jar, in order to prevent dust falling into the 
vessel. The tissues were frequently powdered a second time 
when dry, and they were covered over with strong glycerine, 
the quantity of glycerine being much in excess of the bulk of 
the tissue. The vessel was then covered with a glass lid, and 
the extraction allowed to go on for a period of six to eight weeks. 
At the expiry of that time the contents were filtered through 
fine muslin, pressure being exerted to squeeze out any of the 
juice that remained in the tissue, and occasionally a little more 
glycerine was added to increase the quantity of the fluid. The 
fluid so obtained was a perfectly clear homogeneous fluid, and 
was now ready for experimental purposes. This method, as has 
been shown by Yon Wittich, is a satisfactory one for demonstration 
purposes, but is by no means reliable for research, as the solutions 
contain enzymes in a far from pure state. Still, we know that 
most enzymes are soluble in glycerine, and, moreover, whether 
we are dealing with the pure enzyme or not, glycerine does 
extract it in sufficient quantity to give at all events qualitative 
results when used in digestion experiments. 
The experiments were carried on in an incubator with heat 
regulator, so that any required temperature could be maintained. 
The material consisted of fresh fibrin, starch solution, solution 
of cane sugar, solution of 0*2 per cent. HC1, solution of 1 per cent. 
Xa 2 C0 3 , and the usual chemicals employed as tests in such 
researches. The starch solution was freshly prepared for each 
set of observations. It consisted of 1 grm. of the best rice 
starch dissolved in 50 c.c. of water. The cane sugar solution con- 
tained 1 grm. of sugar in 50 c.c. of water. The fibrin was fresh, 
and washed in running water for at least twelve hours before 
use. 
If X be the name of the extract used, then X was divided 
into the following portions, and submitted to certain tests : — 
1. 10 c.c. of X were added to 20 c.c. of starch solution. These 
two fluids were shaken in a test tube. The test tube 
was plugged, and placed in the incubator at a temperature 
of 38° C., for twenty-four hours. 
The mixture was then tested with Fehling’s solution, 
