226 THE PHENOMENA OF PUTREFACTION 



in practice in so far that by skilfully encouraging its development pit-water very 

 rich in gypsum has been entirely freed from sulphates (CaS0 4 being converted 

 into CaS and FeS) and rendered suitable for 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..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 para- 

 graphs) 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 

 O. F. Miiller. However, when FELIX DUJARDIN (I.), in 1841, undertook to 

 critically examine Ehrenberg'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 animale), and described it as follows : " Form, cylindrical ; length, 

 2-3 p; thickness, 1.0-1.2 /n; frequently united in couples ; exhibiting a tremu- 

 lous movement," the latter being ascribed to alternate contractions and re-expan- 

 sions of the plasma. To these characteristics PERTY (I.) in 1852 added another, 

 viz., the grape-like form peculiar to the zooglcea 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 fer- 

 ments (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 (I.), 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 investi- 

 gators (e.g. B. SANDERSON (I.) in 187:, and E. EIDAM (I.) in 1875) into the 

 physiological conditions of the so-called Bacterium termo are now only of historical 

 interest. On the introduction of plate-cultures into practical bacteriology, pure 

 cultures of the supposed Bacterium termo were soon obtained, and it was then 

 found that this term comprised a number of different species. ROSENBACH (II.), 

 in 1884, was the first to ascertain this fact, and described three distinct species 

 of decidedly putrefactive bacteria, which he named respectively Bacillus sapro- 

 genes /., //., and ///. Rosenbach undertook these researches from a medical 

 point of view, and consequently treated the morphological and physiological sides 

 of the question in a perfunctory manner. Nevertheless, he deserves the credit 

 of having finally banished the designation Bacterium termo from systematic 

 botany ; so that, though the name is still occasionally used, it has now no special 

 import, but merely serves as a convenient synonym for the term " putrefactive 



