THE SAPROPHYTIC BACTEEIA 113 



smell to the decomposing milk. This fermentation, however, never 

 becomes very great, owing to the severely restraining influence on 

 it, of the lactic acid. 



As the higher fungi preponderate only so long as the acidity is 

 high, the bulk of the decomposition is performed by the lactic-acid 

 bacteria. After two or three months, organisms like Proteus vulgaris 

 make their appearance, and complete the decomposition Putrefactive 

 bacteria in the strict sense of the term have very little to do with 

 the decomposition of milk, as the lactic-acid bacteria cannot be in- 

 cluded under this class of bacteria. 



(c) Eggs. The outer covering of eggs is not suflScient to ward off 

 bacterial attacks, as bacteria find no great difficulty in penetrating 

 the shell. Further, bacteria are present even before the shell has been 

 deposited, and consequently even a fresh-laid, egg is never free from 

 bacteria. The decomposition of an egg takes place along one of two 

 lines. In the first, the albumen changes into a whitish-gray or greenish- 

 gray colour, whilst the yolk at the same time gradually turns into 

 a blackish-green slimy mass, which later fuses with the decomposed 

 albumen, the whole forming a pulpy mass which smells very strongly 

 of sulphuretted hydrogen. From this mass one investigator has 

 isolated ten species, all of which have been temporarily included 

 under one name, viz. Bacillus oogenes hydrosulphureus. In the second 

 mode of decomposition, no sulphuretted hydrogen is formed. Both 

 the yolk and the albumen are changed into thin liquids, which 

 later become pulpy and have the same smell as human excrement. 

 The cause of this change has been ascribed to five species of bacteria, 

 all of which have been termed Bacillus oogenes fluorescens. All five are 

 strongly aerobic, and as the shell is penetrable to gases, there is no 

 difficulty in securing an abundant supply of oxygen from the atmo- 

 sphere. The methods for the preservation of eggs will be described 

 in the chapter dealing with the preservation of food-products. 



We cannot in this book enter into a detailed description of the 

 various intermediate substances that are produced in any mass of 

 decomposing matter. The amino-acids, produced by the breaking up 

 of peptones and albumoses, are the first substances to be formed, the 

 chemical constitutions of which are known. From the production of 

 amino-acids to the formation of the end-products almost all the prin- 

 cipal changes can be expressed as chemical equations. The number of 

 intermediate products thus formed is very numerous. Amongst them 

 Iiidol is to be reckoned. This is a foul-smelling substance produced by 

 a number of bacteria in nutrient media containing peptone. As it 



H 



