294 PHENOMENA OF PUTREFACTION. 



various purposes, such as feed-water for steam-boilers, &c. Further 

 particulars on this matter will be found in the treatise referred to. 

 The sulphuretted hydrogen produced by the above-named bacteria 

 is consumed by a special group of fission fungi which will be more 

 closely considered in Chapter xxxv. 



Among the sulphurous products of albuminoid putrefaction 

 mention must be made of mercaptan (C 2 H 5 .SH), which was first 

 detected by M. VON NENCKI and N. SIEBER (II.) in cultures of 

 Bacillus liquefaciens magnus. 



169. The Putrefactive Bacteria. 



In the course of his investigations (frequently alluded to in 

 previous paragraphs) on the micro-organisms in putrescent liquids, 

 Chr. Ehrenberg observed a variety of forms and dimensions. The 

 smallest of them bordered on the limits (Lat. termo} of visibility, 

 and was so minute as to be almost indistinguishable by the aid of 

 the optical instruments then available. On this account he, in 1830, 

 gave it the name of Bacterium termo, and subsequently, in 1838, 

 expressed the opinion that this species is identical with the Vibrio 

 lineola already described by 0. F. Miiller. However, when FELIX 

 DUJARDIN (I.), in 1841, undertook to critically examine Ehren- 

 berg's discoveries, and classified all the (infusorial) micro-organisms 

 devoid of visible organs of locomotion into the family Vibrionia, 

 which comprised the three genera Bacterium, Vibrio, and Spirillum 

 the old name of Bacterium termo was re-applied to this organism. 

 Dujardin also regarded this "infusorium" as the smallest of all 

 living creatures (le premier terme en quelque sort de la serie animate), 

 and described it as follows: "Form, cylindrical; length, 2-3 /A; 

 thickness, 1.0-1.2 [i; frequently united in couples; exhibiting a 

 tremulous movement," the latter being ascribed to alternate con- 

 tractions and re-expansions of the plasma. To these characteristics 

 PERTY (I.) in 1852 added another, viz., the grape-like form peculiar 

 to the zoogloea of this microbe. One year later COHN (V.) also 

 described a like organism. Then when, towards the close of 

 the sixth decade of the century, Pasteur fully explained the 

 theory of specific ferments (originated by Kiitzing), and proved its 

 accuracy by a series of examples, of which lactic fermentation was 

 the first, the inclination to regard putrefaction as the work of 

 a specific fission fungus gradually spread. Hence it was that 

 COHN (L), in 1872, propounded the dictum that "putrefaction is 

 a chemical process excited by rod-bacteria (Bacterium termo). 



The more accurate (physiological) investigation of this process 

 long remained impossible owing to the lack of means for isolating 

 and obtaining pure cultures of its active organism. For this reason 

 the results obtained by different investigators (e.g. B. SANDERSON (I.) 

 in 1871, and E. EIDAM (I.) in 1875) ^ the physiological condi- 

 tions of the so-called Bacterium termo are now only of historical 



