CHAPTER VII 



CHEMISTRY OF BACTERIA 



Some of the most interesting and important manifesta- 

 tions of bacterial life are the chemical changes which are 

 brought about by bacteria. They are so manifold, many of 

 them of such a complicated character and so little under- 

 stood, that it is at present impossible to arrange them in a 

 system, or to classify them in any comprehensive scheme. 

 All that is at present possible is to give an outline of the more 

 obvious chemical manifestations observable during the 

 growth of certain species or of groups of them. 



I. One chemical change frequently exhibited is the power 

 of bacteria to peptonise nutritive gelatine ; this exhibits itself 

 as more or less rapid liquefaction of the nutritive gelatine 

 in which growth is taking place, and as the growth proceeds 

 liquefaction of the whole nutritive medium is effected. 

 Many bacteria have this power : those occurring in water, in 

 the air, in the soil : bacillus fluorescens liquescens, bacillus 

 subtilis, bacillus mesentericus, micrococcus liquescens albus 

 and aureus, several species of sarcina, bacillus prodigiosus, 

 bacillus pyocyaneus, proteus vulgaris ; then many disease 

 germs : bacillus anthracis, the (anaerobic) bacillus of symp- 

 tomatic charbon, of Koch's malignant oedema (anaerobic), of 



