2 BACTERIA. 



within and without the body and the etiology of certain 

 infective diseases, and certain processes of putrefaction and 

 fermentation. At first bacteria were claimed for both the 

 animal and vegetable kingdoms by the workers in each, 

 and the fortunes of war seemed for long to favour the 

 zoologists ; but after a sharp struggle the fission fungi, as 

 they are called, were relegated to the domain of botany, and 

 now for many years the morphology of these organisms has 

 been an object of most careful study by scientific botanists. 

 Bacteria were, however, so minute that it was impossible to 

 study them very accurately with the older microscopes, and 

 for long the group contained very few species, whilst in 

 addition to the fallacies connected with actual observation of 

 size, form, and methods of reproduction, there were others 

 that resulted from the fact that it was impossible, until com- 

 paratively recent years, to obtain what are now known as 

 pure cultivations ; forms that were utterly dissimilar in 

 morphological characters were supposed to be stages of the 

 developmental cycle of the same organism, although they 

 might be, and probably were, really nothing but different 

 organisms that were capable of growing in a common 

 medium. When at length more or less pure cultivations 

 of certain organisms were obtained, botanists were able 

 to study, in some cases very completely, the life-history 

 and morphology of various forms of bacteria, and great ad- 

 vances in bacteriological science were made. Still no very- 

 accurate observations on the functions or physiological 

 chemical processes associated with the life-history of bacteria 

 and allied forms were made, and many of the biological 

 questions, some of which had already been answered as 

 regards animal and the higher vegetable protoplasm, still 

 remained as in a sealed book so far as this lowly vegetable 

 protoplasm was concerned. 



/ In the last ten or twelve years, however, owing to the vast 

 improvements that have been made ia the methods of culti- 

 vation of these organisms, and especially of obtaining what 

 are known as pure cultures, i.e., cultures that contain a single 

 species of organism only, most valuable data as to the func- 

 tions and biological chemistry of these minute specks of 

 vegetable protoplasm have been rapidly accumulated. 



Pasteur's wonderful observations on yeasts first opened 

 up the way for future workers. His practically pure cul- 



