CULTURAL CHARACTERS OF BACTERIA 17 



modified by rapidity of growth, a slowly growing organism form- 

 ing a convex growth of small diameter, which becomes flatter 

 and more spreading with a more rapid development. Again, it 

 is important to decide as to those characters which shall possess 

 the greatest taxonomic value. The more profound chemical 

 changes induced in media probably have more value than the 

 microscopic appearances of growths. Among these are Uque- 

 faction or non-Hquefaction of gelatin, proteolytic action, the 

 fermentation of carbohydrates, diastatic action, the reduction of 

 nitrates to nitrites, the formation of volatile and fixed organic 

 acids, together with the fermentation of definite carbohydrates 

 in the culture media; in the case of the production of lactic 

 acid, whether the latter is optically inactive, or active, and if the 

 latter, whether right or left handed in its action on the polar- 

 ized ray. These and other investigations on the biochemistry 

 of bacterial species should demand greater attention. It means 

 that the bacteriologist must familiarize himself with chemical 

 methods, since in the future the study of the chemical functions 

 of bacteria will form a most important factor in species differen- 

 tiation. 



I. THE TERMINOLOGY OF DESCRIPTIVE BACTERIOLOGY 



An important desideratum in descriptive bacteriology is the 

 adoption of a system of terminology. Many of the descriptions 

 of cultural characters are unnecessarily verbose. A few well- 

 defined terms will suffice to express as much as several sentences 

 of descriptive matter, and with greater exactness. Some exam- 

 ples will suffice. A description of Bact. mycoides reads : " In 

 gelatin stick cultures an outgrowth of branching filaments occurs 

 along the line of puncture, looking like a small fir tree turned 

 upside down." One term, arborescent, will express the phe- 

 nomenon without this unnecessary verbosity, understanding an 

 arborescent growth to be one typically represented by this species. 

 Furthermore, the term arborescent is sufficiently elastic, and yet 



