VITALISTIC THEORY OF FERMENTATION. 15 



point of view, and it was in the course of this study that he examined 

 the mycelia that develop on beer, &c. These consist of masses of 

 elongated cells, to which he gave the name Mycoderma cerevisice. 

 As he fancied they exhibited powers of locomotion, he considered 

 them as belonging to the animal kingdom (animalcula monadina), 

 but, true to his purely descriptive inclinations, he disregarded 

 their physiological properties, and especially their influence on the 

 substratum. Thus the reputation attributed to Desmazieres of 

 having, in 1826, microscopically studied the morphology of the 

 yeast-like cells, to which Persoon had definitely alluded four years 

 earlier, is dissipated by facts. 



On the other hand, a German worker, viz., ERXLEBEN (I.), had 

 already, in 1818, correctly estimated the importance of yeast, in 

 that he asserted it to be a living organism, the vital functions of 

 which are the cause of fermentation. Unfortunately he did not 

 follow up this idea, which was thrown out as a mere occasional 

 remark in his treatise on practical analytical experiments. Other- 

 wise he would, in 1818, have anticipated what was only accom- 

 plished twenty years later, viz., the establishment of the fact that 

 (alcoholic) fermentation is causatively connected with the life 

 (vita) of certain organisms. This was determined, almost simul- 

 taneously, by three investigators working quite independently of 

 each other : Cagniard-Latour in France, and Theodor Schwann 

 and Friedrich Kutzing in Germany. 



The paths by which these three arrived at their common goal 

 differed. The versatile French technicist is known by name to 

 the majority of educated people on account of the siren he in- 

 vented, and which is largely used in the science of acoustics. He 

 also devoted some attention to brewing, and compiled a work on 

 the fermentation of beer. The preliminary studies undertaken in 

 this connection led him to more closely investigate the nature of 

 the "yeast," of which notwithstanding the observations of his 

 two compatriots already mentioned practically nothing was then 

 known. This material he examined with the assistance of the 

 microscope, and laid the results of his researches before the 

 Parisian Academy on June 12, 1837, in a short paper (II.) con- 

 taining the following chief points : 



1. Beer-yeast, instead of being an inanimate chemical substance, 

 as previously supposed, actually consists of small globules which 

 possess reproductive power, and are therefore living organisms. 



2. These bodies appear to belong to the vegetable kingdom, 

 and to reproduce themselves in two ways. 



3. They seem to act upon sugar solution only whilst still 

 living; wherefore it may, with great probability, be concluded 

 that, by their vital activity, carbon dioxide is liberated, and 

 the sugar solution transformed into an alcoholic liquid. 



