DISCOVERY OF ACETIC ACID BACTERIA. 385 



celebrated as a chemical expert on wine, subjected the " mother 

 of vinegar" to chemical analysis, and, because he failed to dis- 

 cover the presence of any ash constituents, thought that it must 

 be regarded as a compound of protein and cellulose. Mulder's 

 statement was refuted in 1852 by R. THOMSON (I.), who showed 

 that a sample (but by no means a pure culture) of "mother of 

 vinegar" contained 94.53 per cent, water, 5.134 per cent, organic 

 matter, and 0.336 per cent. ash. 



The diffusion of new light on this matter was reserved for 

 PASTEUR (XIII.). Taking up anew the question of the origin of 

 acetic fermentation examined by Kiitzing merely from the purely 

 botanical side, and that only cursorily he controverted the 

 opinions of the chemists, and proved, in 1864, that this fermen- 

 tation also is a physiological process, whose inception and main- 

 tenance is bound up with the vital activity of minute fungoid 

 organisms, to which he applied the specific name Mycoderma 

 aceti, first employed by Thomson. Of course, at that time, 

 PASTEUR (XIV.) was not in a position to prepare or use pure 

 cultures, consequently the results of his experiments cannot now 

 be credited with more than the single value of having unim- 

 peachably proved the dependence of acetic fermentation on 

 the vital activity of certain micro-organisms. Pasteur did not 

 determine to what group of living organisms Mycoderma aceti 

 belongs, the botanical, and especially the morphological side of 

 the question concerning him but little ; only, in one place in 

 his treatise, he states that he cannot regard the organism as a 

 bacterium, as was done by Stack in 1863. Nevertheless, we, at 

 the present day, must agree with the opinion of the last-named : 

 the cause of acetic fermentation studied and described by Pasteur 

 can only have been a fission fungus. 



The property of forming mucinous skins on the surface of 

 liquids is not peculiar to the acetic acid bacteria alone, but, on the 

 contrary, is a very general vital phenomenon among fungi. It is- 

 particularly noticeable among a group (which will be considered 

 in the second volume) of budding fungi, which have been named, 

 according to the nature of the medium in which they are found, 

 Mycoderma cerevisice, Mycoderma vini (Fr. fleur de la Here and 

 fleur du vin respectively). Pasteur denied that any of these skin- 

 forming budding fungi have the power of producing acetic acid, 

 but the author refuted this opinion by proving, in 1893, the 

 existence of at least one such species endowed with this faculty. 

 More particulars concerning this will be given in one of the chap- 

 ters of the second volume. At present we are only concerned with 

 the fact that acetic fermentation is a vital manifestation not 

 peculiar to fission fungi alone. 



VOL. I. 2 B 



