Green. — On Vegetable Ferments. 121 
protoplasm must be brought into as close contact as possible 
with the nutrient medium in which the microbe is growing. 
Its extreme susceptibility to acids renders this rather a 
hindrance to the multiplication of the bacillus. An enzyme 
excreted and effecting the changes in the medium without 
such close contact with the organism enables the latter to 
secrete a firmer and more resistant cell-wall, thereby pro- 
tecting it from adverse influences. He bases this hypothesis 
on noting the effects of acids on the organism when grown 
anaerobiotically, or without secreting the enzyme, and when 
cultivated under normal conditions. 
The enzyme in most cases is more resistant to the so-called 
antiseptics than is the bacillus producing it. Most of these 
antiseptic bodies will enable an active ferment-extract to be 
prepared while the organism is kept from developing. Wood 
shows that the cholera-bacillus is an exception, one to two 
drops of a 5 per cent, solution of carbolic acid in 10 cc. bouillon 
destroying the enzyme but not damaging the organism. 
Zymogens. 
Most of the enzymes hitherto described have only been in- 
vestigated with regard to their distribution and behaviour, their 
mode of formation being left undecided. Analogy with similar 
bodies occurring in the animal organism suggests that they ori- 
ginate in the condition of zymogen, or mother of ferment. So 
far as histological evidence is available, their appearance in the 
cells is strikingly like the corresponding process in animal cells, 
pointing to their formation as granules from the protoplasm. 
The existence of vegetable zymogens was first established 
by Vines 1 in his experiments on Nepenthes. He treated some 
pitchers of this plant with dilute acetic acid (1 per cent.) for 
twenty-four hours before extracting them with glycerine, and 
at the same time extracted other similar pitchers with glyce- 
rine without preliminary treatment with acid : the first extract 
possessed greater powers of digestion than the second, leading 
him to infer that, as in the secreting cells of the stomach and 
1 op. cit. 
