io8 Green. — On Vegetable Ferments. 
Underlying the curious stories current among the natives 
as to the powers of these fruits, there has been ascertained to 
exist in each of them a proteo-hydrolytic ferment. The 
Papau was the first to be investigated, and to the labours of 
Wurtz 1 and of Sidney Martin 2 we are indebted for a fairly 
complete knowledge of its properties and powers. Wurtz 
found that in the juice of the stem, leaves, and fruits of this 
plant, an enzyme exists which digests various kinds of proteids. 
It can be prepared by expressing the juice, precipitating 
therefrom the enzyme in a very impure condition by strong 
alcohol, dehydrating the precipitate and extracting it with 
water. Wurtz considered it to be a proteid body; the ex- 
tract containing it was neutral in reaction and became cloudy 
on boiling. Probably his body was by no means pure, 
judging from the method adopted to prepare it. It acted 
rapidly in a neutral medium, dissolving animal proteids, and 
forming chiefly peptones, but also crystals of leucin. 
A much more complete examination of it was made in 
1883 and 1884 by Martin. He prepared it from the com- 
mercial papai'ne obtainable in the market, and found it to be 
intimately associated with proteid matter existing in the fruit 
or latex. In his experiments he used both animal and vege- 
table proteids, and found it capable of digesting both. 
Working on fibrin and on egg-albumin, Martin says that 
the action is one of corrosion of the proteid matter, rather 
than one of solution. In the experiments the fibrin was 
gradually converted into a pultaceous mass, a good deal of 
turbidity accompanying the action, just as in the case of 
digestion of similar material by the trypsin of pancreatic juice. 
The optimum temperature was 35 0 to40°C., but at lower tem- 
peratures such as 15 0 C., it was also active. He agrees with 
Wurtz in finding that it will work in a neutral medium, but 
says that the activity is much greater when a little Na 2 C 0 3 
(about *25 per cent.) is added. Greater alkalinity than this 
is prejudicial, while very slight acidity, even *05 per cent. HC1., 
1 Comptes Rendus, 1879, P* 22 5 > 1880, p. 1379. 
' x Journal of Physiology, vol. V, 1884. 
