THE SAPROPHYTIC BACTERIA 111 



In the case of organisms like Bac. coli communis and Proteus 

 vulgare that attack both proteids and sugars, the proteid-decomposition 

 is hindered very much if much sugar be present in the medium. 

 In such a case, the usual result is a temporary cessation of bacterial 

 activity owing to the production of acids, into which the sugars 

 are transformed. The decomposing material, however, forms now a 

 suitable medium for the growth of moulds and allied fungi, if the 

 supply of oxygen be sufficient. The result of the activity of such 

 organisms, is a still further decomposition of the organic matter, and 

 at the same time a total or a partial removal of the acids. This 

 removal gives the bacteria another chance, with the result that 

 competition among the different kinds once more sets in, and the 

 proteid matter is still further decomposed. This goes on until either 

 unsuitable products are formed or until the amount of acid is once 

 more sufficiently large to prevent further bacterial growth. In the 

 latter case the moulds and other higher fungi will again step in and 

 be again ousted by the bacteria when the acidity has been removed. 



If decomposition takes place in the absence of an adequate 

 supply of oxygen, the products that are formed are of an entirely 

 different character to those that are formed when the supply of 

 oxygen is plentiful. The proteids are not so completely broken up, 

 and such substances as skatol, indol, sulphuretted hydrogen, and other' 

 foul-smelling substances are produced. A good example of such 

 decomposition is that which takes place inside the intestines where 

 anaerobic conditions hold. 



With regard to the fats contained in putrefying matter, they need 

 ,tiot be considered here, as they do not affect the course of putrefaction. 

 We shall obtain a good idea of the course of the changes that take 

 place if we take concrete instances and follow in them the stages of 

 decomposition so far as this is possible. 



(a) Putrefaction of Meat. The aerobic bacteria, which decompose 

 both proteids and sugars, are the first to start decomposition in 

 meat. As there is only about one per cent, of sugar in meat, the 

 production of acids is not great, so that the proteid-decomposition 

 is not appreciably hindered owing to their presence. The organisms 

 that appear first are Proteus vulgaris. Bacillus coli communis, and 

 certain members of the Coccaceae, e.g. Micrococcus pyogenes. These 

 predominate for a time, during which a large amount of proteids 

 is broken down and a very small amount of acidity developed. 

 The smallness of the acidity is to be accounted for, not only by the 

 smallness of the sugar-content in meat, but also by the neutralisation 



