228 THE PHENOMENA OF PUTREFACTION 



generally smaller, the least of them being globular in form and 0.4 p. in diameter. 

 Short rods (0.8 p, long) joined in pairs are frequently encountered. These three 

 species are unique in the bacterial kingdom in point of motile power, which they 

 possess to such a high degree that a solid medium containing only 5 per cent, of 

 gelatin is unable to restrain them, and they make their way across it in all 

 directions. In order to stop this roving motion the gelatin content must be 

 increased to 10 per cent. This peculiarity is not only of physiological interest, 

 but is also decidedly important so far as practical bacteriology is concerned, in 

 that it indicates the futility of employing nutrient gelatin media containing less 

 than i o per cent, of gelatin for the preparation of pure plate cultures of Proteus 

 species. To complete the characterisation of these three species, it should be 

 mentioned that none of them forms endospores, and that their growth may be 

 arrested by depriving them of oxygen, though they do not necessarily die in 

 consequence. They will not thrive in mineral nutrient media, such as those of 

 Cohn and Nageli. When grown in albuminous media, they produce stinking 

 decomposition. A. BRODMEIER (I.) proved that in neutral or alkaline solutions 

 Proteus vulgaris is able to convert urea into ammonium carbonate. He thus 

 refuted the assertions of Leube to the contrary, and confirmed the discovery of 

 Schnitzler and Hofmeister. 



No pretension can be made in the present work of giving a complete descrip- 

 tion of all known forms of putrefactive bacteria, and therefore the examples 

 already cited, being the species most frequently met with, must suffice. More- 

 over, we have already mentioned others of this class in previous paragraphs. 

 One of these, viz., the Bacterium Zopfii, discovered by KURTH (I.) in the 

 stomachs of fowls and shown in Fig. 31, is, according Czaplewski, identical with 

 Proteus Zenkeri. This note appears in an abstract of a work by CH. MOUGINET 

 (I.), who, also, minutely examined a number of putrefactive bacteria. HOLS- 

 CHEWNIKOFF (I.) described a fission fungus closely allied to Proteus vulgaris, 

 which, from its faculty of producing sulphurretted hydrogen, has been named 

 Proteus sulfureus. 



Only one more species will be dealt with here, and that briefly, viz., Bacterium 

 coli commune, which is an invariable inhabitant of the alimentary canal of the 

 human subject (and of all the higher animals hitherto examined), and constitutes 

 the most important of the bacteria present in fseces. This parasite was first 

 described by TH. ESCHERICH (I.) as a slender short rod, 0.4 /* broad, the length 

 varying with the conditions of nutrition and cultivation, but mostly measuring 

 2-3 n, though occasionally it decreases to 0.5 /*. By some authors this fission 

 fungus is named Bacillus coli communis and Colon bacillus. Like the Proteus 

 species, it generally appears as double rods, but its movements are sluggish 

 and laboured. It does not liquefy gelatin. In media containing sugar it can 

 develop even in the absence of oxygen, and liberates a gas which according to 

 FREMLIN (I.) consists of two-thirds carbon dioxide and one-third hydrogen. 

 No development of endospores has hitherto been detected. In its manner of 

 growth in artificial media this organism agrees in many particulars with Bacillus 

 typhi abdominalis. Consequently they are extremely hard to differentiate, and 

 this makes the bacteriological examination of water a particularly difficult opera- 

 tion when the presence of typhus bacilli has to be quantitatively determined. A 

 further complication is imparted by the extreme sensitivity of B. coli commune 

 to modifications in the conditions of cultivation, and by its great tendency to 

 form varieties. For instance, a number of races of B. coli commune are nosv 

 known, which, under certain circumstances, are not merely saprophytic, but also 

 pathogenic. A more detailed treatment of this question would occupy too 

 much of our space, and besides, the matter is fully recorded in Tiemann-G'artner's 

 work on Water Analysis. A synopsis of the most important researches of 



