PATHOGENIC, CHROMOGENIC, ZYMOGENIC BACTERIA 73 



of developing endospores. This definition has not yet been accepted by the 

 majority of bacteriologists ; hence it happens that newly discovered rod-shaped 

 species of fission fungi are still occasionally assigned to the genus Bacillus, 

 although the describer may have no knowledge whatever as to their capability 

 of forming endospores. The author has not considered it within his province to 

 change this nomenclature, and therefore this fact must be borne in mind in 

 perusing the present work. It should also be remembered that in the following 

 paragraphs the generic name Bacillus Hueppe's definition notwithstanding 

 means nothing more than that the species of bacterium so entitled exhibits, 

 preferentially and under normal conditions, the bacillus form of growth. 



A comprehensive collection of the relative dimensions and forms charac- 

 teristic of growth in various nutrient media, &c., of about three hundred species 

 of fission fungi was prepared by EISENBEUG (I.), and may be advantageously 

 employed as an aid to determining whether any species under examination is 

 identical with any known species. A descriptive table of eighty-seven of the 

 bacteria of most frequent occurrence in drinking and utilisable water is given 

 by ADAMETZ (I.). Reference may also be made here to the very valuable book 

 of TIEMANN and GAHTNER (I.) in connection with the bacteriological analysis 

 of water. FRANKLAND and WARD (I.) give a comprehensive account of the 

 literature published up to the year 1882 on the bacteria occurring in natural 

 and mineral waters, and a comparative investigation into the distribution of a 

 number (twenty-eight) of well-known bacterial species in various well-waters has 

 been made by W. MIGULA (III.). 



70. Pathogenic, Chromogenic, and Zymogenic Bacteria. 



The attempts hitherto made to obtain a method of classification of bacteria 

 have always been restricted to the morphology of the organisms themselves. It 

 will now be well to remember that the attention of Applied Mycology is pre- 

 ferentially directed to the influence exerted by the fungi on their nutrient 

 media. The interest aroused by these organisms has always, from the outset, 

 had its practical side. Bearing this in mind, it will be readily conceivable that, 

 long before the establishment of Cohn's first classification, there had appeared in 

 the literature of the subject a division of bacterial species into three main 

 groups : pathogenic, chromogenic, and zymogenic bacteria. 



It is quite unnecessaty to remark that this grouping is just as faulty as the 

 division of the Schizomycetes into cocci, bacilli, and thread bacteria. Neverthe- 

 less it was exceedingly convenient, as it was based on some well-marked primary 

 characteristics. If the fission fungus in question excited any form of disease in 

 men or animals, it was referred to the pathogenic group ; if it possessed the 

 faculty of producing colours, it was relegated to the category of chromogenic 

 bacteria ; and if it exhibited a capacity for effecting those chemical changes which 

 were comprised in the term "fermentation" ( i), it was considered as zymo- 

 genic. A strict adherence to this method of partition is impracticable, because 

 there are some bacteria which, on account of their range of activity, would 

 have to be placed in two, or even all three of these classes. A large number of 

 examples could be adduced in support of this assertion; it will be sufficient 

 to cite merely a single one, viz., Staphylococcus pyogenes aureus, the cause of 

 osteomyelitis (bone caries), and therefore pathogenic. However, since it also, as 

 its name implies, produces a golden-yellow colouring matter, it is also chromo- 

 genic ; and, finally, from its power of setting up lactic fermentation in suitable 

 nutrient media, it is therefore also zymogenic. 



From this example it will be evident that the domains of Pathological and 

 Technical Mycology cannot be rigidly kept separate. On the contrary, their 



