120 Proceedings of the Royal Society of Edinburgh. [Sess. 
It is obvious from the whole nature of the experiment, and from the 
manner in which the different samples were obtained, that a certain amount 
of irregularity must be expected in the results. Such fluctuations, however, 
have not been found to be nearly so serious as was anticipated. The fact 
that the maximum degree of activity is reached somewhat later in the third 
than in the first and second experiments is easily explained by the fact that 
an entirely different variety of barley was used, while the other irregularities 
are so small that they cannot obscure the evidence of the experiments, to 
the effect that, of the two forms of activity, the one rises sharply from 
nothing in the ungerminated seed till it reaches its maximum, after which 
it remains fairly constant during the remainder of the experiment. On the 
other hand, the activity in the second case rises comparatively slowly from 
slightly above zero in the ungerminated seed till it reaches its maximum a 
few days later than in the former case, after which it rapidly falls again. 
The presence of both of these forms of activity in germinating barley 
having been thus demonstrated, it seemed desirable to investigate the 
existence of similar enzymes in material of widely different origin. For 
this purpose the strongly proteolytic and peptolytic enzyme, Bromelin, 
contained in the juice of the fruit of Ananassa sativa, was selected. In 
order to make the experiments more complete, it was decided to carry out 
parallel digestions, using as substrate in one case the alcohol-soluble 
protein of wheat, and in the other a solution of Pepton Witte. 
The digestions were carried out partly in presence of the natural acidity 
of the juice, partly with a juice that had been neutralised, and partly with 
a portion made slightly alkaline with sodium bicarbonate. In each case 
5 c.c. of the juice was employed, and three digestions were carried out with 
each substrate and each reaction. 
The following series of digestions were accordingly prepared : — 
(a) 2 grms. protein + 5 c.c. water + 5 c.c. juice. 
(b) 5 c.c. 4 per cent. Pepton Witte solution + 5 c.c. juice. 
( c ) 5 c.c. 10 per cent. Pepton Roche solution -f 5 c.c. juice. 
As usual, half of the digestions (a) and ( b ) were precipitated before 
digestion with tannic acid ; the others, along with (c), being digested at 37°. 
After twenty-four hours (a) and ( b ) were withdrawn and precipitated, the 
nitrogen contents of the filtrates estimated, and the amount of peptolysis ex- 
pressed as before. The results are given in the following table, and show that 
a very strong proteolysis and peptolysis had taken place. The corresponding 
Pepton Roche digestions, however, showed no deposit of tyrosin, even after 
three weeks’ incubation, and it is therefore safe to conclude that bromelin 
does not decompose this polypeptid. Whether an enzyme capable of doing 
