632 BEPOKT— 1887. 



organised matter presents problems almost as difficult of solution as those relating 

 to their formation and building up ; that is to say, the phenomena observed do not 

 apparently obey the same laws as those prevailing in the inorganic world. When I 

 began my chemical studies the difference in this respect between mineral and 

 organic compounds was less clearly seen than at present. The conversion of alcohol 

 into acetic acid, the putrefaction of animal and vegetable matter were thought to 

 be simply due to oxidation ; they were phenomena, it was supposed, exactly similar 

 to the rusting of iron, the tarnishing of metals, the fading of colours. That a third 

 body was required to initiate and continue the process of decomposition, that 

 organic matter in contact with purified air would remain unchanged for any length 

 of time — was not known nor suspected. I am not quite sure whether spontaneous 

 decomposition — i.e. the splitting up of a complex body without the intervention of 

 an external agent — might not at that time have been considered possible. In order 

 to explain the phenomena of fermentation, the decomposition of sugar into alcohol 

 and carbonic acid, for instance, we had only the theory of contact — devised by Ber- 

 zelius and Mitscherlich, the Litter of whom used to expatiate on the subject at great 

 length in his lectures. When this ghost of a theory was laid by Liebig, who suggested 

 an intelligible explanation of the phenomena in accordance with the facts then 

 known, it was felt to be quite a relief, as affording a resting-place — if only a tem- 

 porary one — for the mind. The brilliant researches of Pasteur, which have thrown 

 so much light oa the action of the insoluble organised ferments, I need only refer 

 to, as they are so widely known, even outside scientific circles ; and since also in- 

 vestigations such as his cannot be discussed without some reference to biological 

 questions, which cannot be entered on here. I will confine myself therefore to a 

 few remarks on the unorganised or soluble ferments, one of which I had occasion 

 to examine when engaged in investigating madder and its colouring matters. These 

 ferments, the type of which is diastase — a substance found accompanying starch in 

 the seeds of plants — are soluble in water, perfectly neutral, devoid of all definite 

 form, and though apparently inert, able when acting within the sphere in 

 which Nature has placed them to cause changes and decomposition of the most 

 profound character. Their action excludes everything in the shape of vitality, and 

 yet it is as mysterious and unaccountable as anything that the vitality of tb© 

 organised ferments is able to effect. Indeed, in vegetable, and especially animal, 

 organisms they seem expressly intended for the attainment of certain ends necessary 

 for the well-being, or even the existence, of the organism, insomuch that it has 

 been supposed, with some show of reason, that it is to bodies of this class existing 

 within the cells of organised ferments, but not separable by any means at our 

 disposal, that the changes produced by the latter are really due. 



A great deal of attention has been paid to the products and results of 

 fermentation, but very little hitherto to the modus operandi of the ferment.s 

 themselves, and j'et this seems to me to offer a wide field for interesting research, 

 especially in the case of those of the soluble class, which are easily prepared, and 

 can be manipulated in the laboratory like any chemical substance without the 

 tedious precautions and preliminary operations necessary in the case of the 

 organised ferments. In what way, it may be asked, do these soluble ferments 

 produce the effects peculiar to them ? Is the action essentially chemical, or is it 

 due to physical causes as well ? Is tlie quantity of fermentable matter acted on by 

 a certain quantity of ferment unlimited in amount, or are there limits to that 

 amount somewhere ? Does the ferment itself undergo any change during the 

 process of fermentation, or is it the same afterwards as before and capable of 

 acting on fresh quantities of fermentable matter ? When a ferment is replaced by 

 a strong mineral acid, the products of decomposition being the same, is the modus 

 operandi in both cases alike, or must a different explanation be in each case 

 sought ? These questions have never been satisfactorily answered, and await 

 solution. I know of only one attempt to show what actually takes place during 

 a process of fermentation set up by a soluble ferment. 



The experiments of Wurtz * on papain, the soluble ferment of Carica papaya, 



' Comjites Beiidiis, 91, 787. 



