ANAEROBES WHICH EXCITE PUTREFACTION. 385 



Proteus Zenkeri (Hauser). 



These are bacilli *4 p. in breadth, and of an average 

 length of 1'65>. ; sometimes the forms are rounder, at 

 other times longer. After inoculation on gelatine a' 

 layer, which towards the periphery becomes thinner like 

 the steps of stairs, is formed around the point of inocu- 

 lation, and from the margin of this layer numerous 

 threads and rods begin to pass out;. after 24 hours we 

 find large numbers of moving islands, composed of rods 

 and threads, presenting exactly the same appearance as 

 in the case of Proteus mirabilis. The deposit becomes 

 gradually thicker and opaque ; but liquefaction of the 

 gelatine does not occur (or only quite at the surface).' 

 The formation of spirilla and spirulina are seldom 

 observed. Cultivations in gelatine and blood serum do 

 not show any marked development of smell ; meat in- 

 fusion, on the other hand, is decomposed with the pro- 

 duction of a strong smell. In its other effects Proteus 

 zenkeri resembles the species previously described. 



Anaerobes which excite putrefaction. 



In a great variety of putrefying mixtures, as also in 

 the intestinal contents, in the buccal secretions, &c., 

 a peculiar want of correspondence is observed between 

 the numerous bacteria which are evident under the 

 microscope, and the species which can be isolated by the 

 ordinary methods of cultivation. As a rule, by the 

 latter methods only a few colonies are obtained, or the 

 nutrient soil remains completely sterile, even after 

 several days, and in spite of all sorts of variation's in the 

 composition and temperature. This absence of bacteria Part played by 

 which can be cultivated appears to be due to a consider- j n 



able extent to the fact that many of the species of factive 



process. 



'bacteria which usually take part in the putrefactive pro- 

 cess are anaerobes, and hence do not grow under the 

 ordinal^ conditions of cultivation. The spores of these 

 bacilli are probably very widely distributed, and almost 

 always enter putrefying mixtures. As soon as the 



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