THE RESEARCHES OF THEODOR SCHWANN 13 



did not indubitably establish the vegetable nature of yeast. The accomplish- 

 ment of this task, and the attribution of this organism to its proper position in 

 the system of Botany, formed the subject of a treatise published by SCHWANN (I.) 

 in the first half of 1837, i.e. contemporaneously with Cagniard's paper. 



In following up the results of his researches on spontaneous generation, 

 Schwann studied beer-yeast, and found that the individual globules, of which the 

 mass was seen under the microscope to consist, frequently became united into 

 chain-like or laterally branching bands, and presented to the eye an appearance 

 greatly resembling that of many already well-known multicellular fungi. It 

 was not this discovery alone, however, but rather their mode of reproduction, 

 which induced Schwann to consider these bodies as of a vegetable nature. In 

 this process the globule pushes out from its interior a small nodule, which 

 Schwann was able to observe develop to its normal dimensions. " Observation 

 of its growth leaves no doubt as to its vegetable nature, since animals do not 

 reproduce themselves in this manner." The rate of reproduction of the globules 

 kept pace with the increasing briskness of the fermentation, so that Schwann 

 came to the opinion that it was highly probable that the development of the 

 fermentation was induced by that of the organism. 



" Vinous fermentation must therefore be regarded as the decomposition 

 occasioned by the sugar fungus extracting, from the sugar and a nitrogenous 

 body, the materials necessary to its nutrition and growth, whereby such elements 

 of these bodies (probably among other substances) as are not taken up by the 

 plant unite, by preference, to form alcohol." 



This discovery was communicated by Schwann to his friend and colleague, 

 Professor Meyen, who tested and confirmed it, " .stating with reference thereto, 

 that the only doubt arising was whether the organism in question was an alga or 

 a thread fungus, the latter seeming the more likely by reason of the absence of 

 green pigment." Thus yeast was recognised as a fungus, and, from its capacity 

 of fermenting sugar, was designated sugar fungus : whence the current generic 

 name, Saccharomyces Meyen. 



According as such a sugar fungus was found active in beer- wort or wine-must, 

 it was called by the specific name of S. cerevisice or S. vini, which names remained 

 in general use in their original significance until REES (I.) in 1870 proposed a 

 system of differentiation which will be more fully noticed in a subsequent 

 paragraph. 



As follows from the remarks already made, the name "yeast" applied merely 

 to one particular group of ferments, viz., those producing alcoholic fermentation. 

 For a considerable period after Cagniard's discovery, however, it was used indis- 

 criminately for all ferments. Thus, for example, Pasteur speaks of the " yeast " 

 of lactic fermentation, meaning thereby Bacteria ; and even in 1879 Nageli, the 

 investigator of the fission fungi, refers in his " Theory of Fermentation " to the 

 " yeast " of putrescent urine. This misuse of the term has been abandoned, and 

 the name " yeast " is now only employed when speaking of the budding fungi 

 that excite alcoholic fermentation. 



14. Friedrieh Kutzing-'s General Theory of Fermentation. 



The views promulgated, by this German worker in the field of Vegetable 

 Physiology and the Algae were in harmony with the spirit manifested in the 

 " Elements of Philosophic Botany." 



Published almost simultaneously with the above-mentioned communications 

 of Cagniard-Latour and Th. Schwann though actually compiled at a much 

 earlier date (before 1834) Kutzing's treatise (I.) on this subject surpassed 

 those of his two colleagues in more than ore particular. The value of his 



