KNf)\VLI.I)r,K 



Mav. 1912. 



of sugary liquids into alcohol and carbon dioxide. 

 Wc speak yit of beer and ale as being "fcrniented" 

 beverages. In the early years of the nineteenth 

 centnrv the cause of this fermentation was beginning 

 to be attriliuted to tlic presence of the yeast-piant or 

 Torula [Siicchiimiiiyccs Ccrcvisiiw). This small 

 fungus had intleed been describeil by the indefatig- 

 able Leeuwenlioek. as early as 1675, in the deposit 

 below a fermenting liquid: no use of this fact was 

 made, however, until abt)ut one hundred and si.xty 

 \ears later, w hen Schwann and Caignard de la Tour, 

 in 1838, demonstrated that these minute bodies were 

 "cells " of vegetable origin and grew abundantly in 

 solutions of sugars. It was natural to connect the 

 presence of these minute fungi with the occurrence 

 of fermentation, but the biologists had to contend 

 against the jjrestige of the great Swedish chemist 

 Berzelius w ho held that fermentation w as essentialh' 

 a chemical affair due to " catalysis." 



Liebig. in 1848. admitted that the yeast-plant 

 might be a link in the chain of causal antecedents 

 in the fermentation. The essence of his view con- 

 sisted in this, that fermentation was a disturbance 

 in the molecular structure of the sugar, of such a 

 kind that under the influence of a cataKst the com- 

 plex molecule fell apart into the simpler ones of 

 succinic acid, alcohol and carbon dioxide. He com- 

 pared it to the " catalytic "' action of metallic 

 platinum black, which causes hydrogen peroxide to 

 be reduced to water and '" nascent " hydrogen, in 

 other words, to be chemicallv broken down. The 

 platinum was a catalxst, it was not changed in the 

 process. 



For a tin)e the ortluidcjx view was that of the 

 chemists: fermentation was "catalytic,"' a view 

 which in 1850 explained nothing; but Berzelius 

 and Liebig had said it was catalytic, and therefore 

 it must be so ! 



But the biologists on continuing to studv the 

 subject found that the more acti\e the fermentation, 

 the more rapidly the plants grew, that the higher 

 the temperature, up to a certain point, the more 

 active was the fermentation, but that boiling the 

 liquid put an end to the whole process. Freezing 

 the licjuid arrested witliout destroying the ferment. 

 All this looked ver\- like life, albeit the living things 

 were invisible to the unaided eye. The conclusion 

 seemed irresistible that as the fermentation was due 

 to the yeast-plant, the plant itself might be regarded 

 as a ferment, a living ferment, an organised or in- 

 soluble ferment, to distinguish it from a ferment 

 like pepsine, which seemed to belong to another 

 class non-living, unorganised, soluble. For many 

 vears these two siiecies of ferments were recognised. 

 About 1879 the physiological chemist, Kiihne of 

 Heidelberg, suggested the name Enzymes or 

 Zymins for the soluble ferments, the secretions of 

 living cells. 



The classical experiment of Helmholt/. in 184.5, 

 seeined to demonstrate very simply that alcoholic 



fermentation was due to an insoluble ferment. He 

 placed .some boiled grape-juice in a bladder, which he 

 immersed in a vat of fermenting grape-juice: after a 

 certain time the contents of the bladder were f(jund 

 not to have fermented, therefore the ferment was not 

 so soluble as to pass thnnigb the bladder used. 

 Later it was shewn that the ferment could be 

 excluded by cotton-wool. 



Helmhoitz, others, and finally Tyndall in this 

 country, made it certain that fermentation was not 

 due to the presence of air or of oxygen, as some of 

 the chemists had thought possible. Fermentation 

 and putrefaction were alike vital, for, as time went 

 on, it appeared that what applied to the former 

 seemed equally to apply to the latter. 



Dead matter, it seemed, would not change its 

 j)hysico-chemical state unless ferments now identified 

 as microscopic saproplntes could gain access to it. 

 Putrescible matter boiled did not putresce but 

 remained indefinitely in the status quo ante until 

 micro-organisms were permitted access to it, when it 

 promptly decomposed. These micro-organisiris were 

 organised ferments, some of which needed oxygen 

 (aerobic), some of which did not need oxygen 

 (anaerobic) and some of which could live w ith or 

 without oxygen (facultative) : this classification was 

 due to Pasteur (1857-61). 



Dead matter putrefied because it was invaded by 

 organised ferments which broke it down into 

 chemical substances (amides and amino-acids). 

 simpler than the proteins (albumins) of which it 

 was composed at the moment of death. Thus post- 

 mortem putrefaction was directly due to the presence 

 of life ; if the air going to putrescible material was 

 previously passed through a red hot tube, so that all 

 micro-organisms were burnt out of it, the material 

 did not putrefy. 



Before long, bacteria, rod-like forms, were found 

 to be the vera causa of putrefaction : bacteria of 

 other shapes were found to be the cause of many 

 infectious diseases thenceforth called " ;iymotic." 

 that is, fermentative. Disposal of the dead — 

 vegetable or animal — is therefore the duty of the 

 humblest species of plant life, the organised 

 ferments. 



For many years the sharp distinction between the 

 organised and unorganised ferments was maintained 

 bv biologists : but in course of time it became 

 apparent that the organised, or insoluble, ferments 

 could, in realitw carry out the chemical changes 

 peculiar to them only by means of something 

 secreted 1)\- them through their cellulose cell-walls. 

 Obviouslv if no interchange of material went on 

 between the protoplasm inside the cell-wall and the 

 sugar outside, then the living plant cell could not 

 influence or alter the state of the sugar in any way 

 whatever, for in histologv we do not believe in 

 "action at a distance" If the lell-niembrane was 

 absoluteh' impermeable, then the yeast was exactly 

 as an inert body might be in the sugar. 



( To he aiiitiiiiuil. 



