274 M. H. Hoffmann on Fermentation. 



and the matter removed is examined by the microscope, the 

 same spores which occur in the expressed juice of the fruit are 

 recognized, mixed with impurities of all sorts ; the brown spores 

 of Stemphylium and Cladosporium, and colourless fragments of 

 Oidium, Monilia, Torula, &c. If the matter scraped off be placed 

 in distilled water, and protected from all access of dust from 

 without, there will be at the end of twenty-four hours dense 

 groups of germinating filaments, and numerous cells of yeast in 

 every stage of budding and fragmentation, and with all the 

 varieties of form which characterize the yeast of the juices of 

 fruits. Infusoria are also frequently met with. The expression 

 yeast is therefore a collective denomination, and not the name of- 

 a species of plant. 



2. The cells of yeast from beer or spirit in fermentation are 

 generally more similar than those of vegetable juices which have 

 undergone no boiling; nevertheless they are not^only round or 

 oval, but also cylindrical. To ascertain what they really are, two 

 methods may be adopted. The first, which has already fre- 

 quently been employed, consists in cultivating yeast, and exa- 

 mining what forms of plants it gives origin to. This is the 

 method employed by Kiitzing, who obtained from it some Sporo- 

 tricha and a Mucor. The second, in which the yeast is pro- 

 duced directly by means of the fungi which are presumed to be 

 its cause, was employed by M. Bail ; he made use of Ascophora 

 elegans, a species of Mucor , and Penicillium glaucum ; and M. 

 Hoffmann states that he cannot but confirm the results obtained 

 by these experiments. 



The observations of M. Hoffmann were made on a large scale 

 in breweries, and on a small scale in cultivations of small por- 

 tions of yeasts. In the breweries, large tufts of Penicitlium 

 glaucum make their appearance on the yeast which has been 

 thrown out ; Penicillium breve, Corda, and Ascophora elegans, are 

 also seen, but in smaller quantities. By cultivation on a small 

 scale, taking all possible precautions to prevent the access of 

 spores from without, M. Hoffmann has observed the development 

 of the fungi above mentioned, together with Periconia hyalina. 

 His experiments were made by pouring a few drops of water into 

 a test-tube inclined obliquely, placing in it a few fragments of 

 fresh yeast, and stopping the mouth of the tube with wadding to 

 prevent the access of any impurities from without. He soon saw 

 the yeast produce mycetoid filaments. 



To ascertain that beer-yeast is only the product of these little 

 Fungi, which are so common everywhere and in all climates, 

 M. Hoffmann placed in one of his tubes a solution of sugar, 

 which does not ferment by itself, together with spores of Peni- 

 cillium glaucum, shook the whole strongly, and then placed the 



