Oyi the Theory of the Process of Fermentation. 161 



I shot two specimens of this very beautifully but subdued- 

 coloured Sihia in April last, when making the ascent of the 

 peak of Khiinho, Eastern Burrail range, Ndga Hills, at about 

 8000 feet. The bird appeared pretty numerous, in companies 

 of four to six or eight, haunting the tops of the rhododendron 

 trees, then in full bloom, busily engaged searcliing for insects 

 in the flowers, and their forehead, chin, and throat were 

 covered thick with the pollen. 



In the general distribution of the coloration and form it 

 resembles S. gracilis^ extremely common in the same locality, 

 but seldom seen there above 6000 feet. 



XX YI. — On the Theory of the Process of Fermentation.. 

 By Dr. H. Karsten. 



Cagniakd de Latour in 1836 recognized alcoholic fermen- 

 tation as a physiological process dependent upon living crea- 

 tures ; and I subsequently (in the ' Bot. Zeitung ' for 1848 and 

 1849) indicated the pathological nature of yeast, i. e. that the 

 yeast-cells were not true species of plants, as was supposed by 

 Latour (and by Persoon, 1822), but pathological organizations. 

 This view is now, after long discussion, making some way, 

 in opposition to the opinion maintained by the majority of 

 chemists (following Liebig) that fermentation is a purely che- 

 mical process quite independent of any vital action. 



Although in 1870 Liebig admitted that alcoholic fermenta- 

 tion is dependent on the presence of living yeast-cells, he en- 

 deavoured, nevertheless, to preserve his previous opinion to a 

 certain extent, by assuming that it was the fluid contents of 

 the yeast-cells which eff'ected the decomposition of the sugar, &c. 



In accordance with the processes of decay in Avhich the 

 oxidation of the albuminous materials transfers itself to the 

 neighbouring carbon compounds (a view, the incorrectness of 

 which I demonstrated in ' Poggendorfl''s Annalen,' 1860), the 

 process of fermentation is supposed to be dependent upon the 

 decomposition of albuminous unorganized substances (outside 

 the cell according to Liebig's former opinion, but within it ac- 

 cording to his present view), which then also seizes upon the 

 surrounding molecules of complex carbon compounds. 



But that even this last conception does not accord with the 

 true nature of the process, and that the products of fermentation 

 loere generated by the vegetating membrane of the yeast-cell and 

 not by its fluid contents, had already been demonstrated by 

 me in my memoir on the Chemistry of the Vegetable Cell 

 in 1869. 



