PUTREFACTION. 613 



materials as the result of putrefaction. We can only 

 employ definite chemical formulae for each kind of putre- 

 faction occasioned by a definite micro-organism. 



The putrefaction which occurs spontaneously shows Spontaneous 

 very great differences, according to the bacteria which pl 

 are accidentally present, and according as the conditions 

 of existence are at the time more favourable for one 

 or other species. The kind of organisms which gain 

 the upper hand at the commencement of the process 

 depend on the concentration, the chemical composition, 

 the reaction, and the temperature of the putrescible 

 materials ; in the course of time, and under the influence 

 of gradually extending putrefaction, these external con- 

 ditions alter completely; from neutral bodies others can 

 arise which cause an acid reaction ; by the decomposition 

 chiefly of nitrogenous molecules and the formation of 

 ammonia the alkalinity of the material may be increased ; 

 the relation of the individual chemical materials alters, 

 because one kind is broken up to a greater extent than 

 another. Thereby the most favourable conditions of 

 existence are again provided for other kinds of bacteria ; 

 and thus the spontaneous putrefaction consists of a series 

 of decompositions, not as a rule following any definite 

 order, but dependent on individual conditions which 

 cannot be controlled, these decompositions being caused 

 by various different kinds of bacteria, and kinds which 

 act in the most various ways. At the commencement 

 of putrefaction we usually observe several kinds of micro- 

 cocci and also large bacilli; in the later stages we find 

 in addition masses of short bacteria; on the surface of 

 the mixture forms seem to predominate which were for- 

 merly described under the name of bacterium termo, 

 and of these it appears from plate cultivations that bacil- 

 lus fluorescens liquefaciens forms the largest numbers. 

 Nor must we forget that numerous forms of bacteria 

 which have no fermentative action, or which do not find 

 a suitable material for the development of their fermen- 

 tative activity, establish themselves in putrefying mix- 

 tures, though it is true that at a later period, when 

 energetic fermentation is present, the organisms which 



