THE ORGANISMS IN YEAST. 227 



A much more objectionable organism which is frequently 

 to be found is the acetic ferment, is shown in the Plate at No. 

 7, as seen under the i — lo in. objective. Under a low power 

 it is visible simply as a thin rod or thread, but the higher power 

 reveals an appearance of segmentation. By the agency of these 

 filaments, the alcohol of beer or wine in which they appear, is 

 converted more or less into acetic acid, and whilst they are dreaded 

 by the brewer, and considered by him as a ferment of disease, they 

 are utilised as an industrial agent by the vinegar-maker, whose 

 mucilaginous ferment consists essentially of them, and I should 

 therefore describe them as the Mycoderma aceti\ had this name not 

 been already applied by Pasteur to another form ; hence, to avoid 

 confusion, I use the term, acetic ferment. From the peculiar 

 movements of these rods, especially at their extremities, I am 

 incHned to think that they are provided with flagella, but am not 

 aware that any observation of them has been recorded. These 

 organisms also multiply by transverse fission, and although I have 

 seen some appearances indicative of the formation of spore-like 

 bodies, I am by no means inclined to advance any opinion as to 

 any such means of increase. The sediment of beer or porter 

 which has become somewhat acid will always afibrd a plentiful 

 supply of this organism, which may be cultivated in a little thin 

 wine or beer. An intruder more rarely seen among the Yeast-cells 

 is the Bacillus sicbtilis, the celebrated Bacillus of the hay infusions, 

 or, at any rate, an organism precisely similar to it in all respects, 

 by which butyric fermentation is induced. It is shown in the 

 Plate at No. 9, and is too well known to need a detailed descrip- 

 tion. Messrs. Dahinger and Drysdale, by the use of extremely 

 high powers and very careful illumination, have satisfied themselves 

 that this organism is possessed of flagella, and their well-known 

 researches render it probable that such appendages are general 

 among the Saprophytes at some stage of their existence. 



The only remaining varieties of organised ferments likely to be 

 met with associated with the Yeast-cell are theMycodernia cerevisia^ 

 the mould which so quickly forms on the surface of malt infusions 

 exposed to the air, and which when submerged acts as an alcoho- 

 lic ferment — it is shown at No. 1 1 on the Plate ; the Saccharoniyces 

 apimlatus (No. 12), a small cell, inducing a peculiar acid change 



