Licence: In copyright
Credit: Alcoholic fermentation / by Arthur Harden. Source: Wellcome Collection.
![contact with the air, provided only that it was raised to the tempera- ture of boiling water at short intervals of time. Gay-Lussac’s opinion was that the ferment was formed by the action of the oxygen on the liquid, and that the product of this action was altered by heat and rendered incapable of producing fermentation, as was also brewer’s yeast, which, however, he regarded, on account of its insolubility, as different from the soluble ferment which initiated the change in the limpid grape-juice. Colin, on the other hand [1825], recognised that alcoholic fermentation by whatever substance it was started, resulted in the formation of an insoluble deposit more active than the original substance, and he suggested that this deposit might possibly in every case be of the same nature. So far no suspicion appears to have arisen in the minds of those who had occupied themselves with the study of fermentation that this change differed in any essential manner from many other reactions familiar to chemists. The origin and properties of the ferment were indeed remarkable and involved in obscurity, but the uncertainty re- garding this substance was no greater than that surrounding many, if not all, compounds of animal and vegetable origin. Although, how- ever, the purely chemical view as to the nature of yeast was generally recognised and adopted, isolated observations were not wanting which tended to show that yeast might be something more than a mere chem- ical reagent. As early as 1680 in letters to the Royal Society Leeuwen- hoek described the microscopic appearance of yeast of various origins as that of small, round, or oval particles, but no further progress seems to have been made in this direction for nearly a century and a half, when we find that Desmazieres [1826] examined the film formed on beer, figured the elongated cells of which it was composed, and described it under the name of Mycoderma Cerevisiae. He, however, regarded it rather as of animal than of vegetable origin, and does not appear to have connected the presence of these cells with the process of fermentation. Upon this long period during which yeast was regarded merely as a chemical compound there followed, as has so frequently occurred in similar cases, a sudden outburst of discoverv. No less than three observers hit almost simultaneously upon the secret of fermentation and declared that yeast was a living organism. First among these in strict order of time was Cagniard-Latour [1838], who made a number of communications to the Academy and to the Societe Philomatique in 1835-6, the contents of which were collected in a paper presented to the Academy of Sciences on 12 June,](https://iiif.wellcomecollection.org/image/b29808765_0015.jp2/full/800%2C/0/default.jpg)
