88 



SCIENCE 



[N. S. Vol. XXXIX. No. 994 



genera, is concerned, we have also, I be- 

 lieve, plenty of information which if prop- 

 erly digested would make it possible to 

 arrive at reasonable and helpful results. 

 With these large groups no special statisti- 

 cal study is generally necessary, for the 

 chief characters of the major types are well 

 established. All that is needed is interpre- 

 tation, but interpretation based on a view 

 of all the available facts and on a sound 

 conception of biological principles. Until 

 recently the only attempt at a general 

 classification of the bacteria based on a com- 

 mon-sense interpretation of all the char- 

 acteristics of the organisms is that pre- 

 sented by Fliigge (1896), the chief value 

 of which lay in the classification of the rod- 

 shaped bacteria into 22 groups, almost all 

 of which appear to represent natural ag- 

 gregations of allied types. For example, 

 we all recognize that the aerobic spore 

 formers, the anaerobic spore formers, the 

 colon-typhoid group, the nitrifying organ- 

 isms, the fluorescent bacteria, and the 

 group of diphtheria and tubercle bacilli 

 constitute real groups of related organisms. 

 Four years ago a more ambitious attempt 

 at a fundamental analysis of the syste- 

 matic relationships of the whole group of 

 bacteria was made by Professor Orla Jen- 

 sen, of the Polytechnicum of Copenhagen 

 (1909). Professor Jensen with good rea- 

 son discards the purely morphological basis 

 of classification and in particular the dis- 

 tinction based on the presence or absence 

 of flagella. The arrangement of flagella 

 when they are present, on the other hand, 

 offers a convenient index of other more im- 

 portant differences and Professor Jensen 

 gives his two orders of bacteria the 

 names of Cephalotrichinae (monotrichous 

 or lophotrichous) and Peritrichinse (peri- 

 trichous). The Cephalotrichin£e, deriv- 

 ing their life energy almost entirely from 

 oxidative processes, are all water or 



moist earth forms, with the exception of a 

 few peculiar plant and animal parasites 

 and for the most part grow badly or not at 

 all on ordinary organic media, and spores 

 are never formed. The series begins with 

 the Oxydobacteriaceffi, including the most 

 primitive bacteria, which oxidize methane 

 and carbon monoxid, the nitrifiers, the 

 acetic acid bacteria and the Azotobaeter 

 group. Then follows the Actinomyces 

 family which includes the root nodule bac- 

 teria and the mycobacterium (tuberculosis) 

 group. The collocation of the latter forms 

 is startling at first, but their morphology, 

 their oxygen requirements and their unique 

 pathological relations, almost symbiotic by 

 contrast with the quick toxic action of 

 other pathogenic bacteria, offer some evi- 

 dence of real relationship. The third, 

 fourth and fifth families are the Thiobac- 

 teriaceas (the sulfur bacteria), the Rhodo- 

 bacteriaceiB (the red or purple sulfur bac- 

 teria) and the Trichobacteriacese (Cla- 

 dothrix, Grenothrix, Beggiatoa, etc.) which 

 are clearly natural groups. The last two 

 families, the Luminibacteriacefe and the 

 Reducibacteriaceffi, are typically denitrify- 

 ing organisms which form a connecting 

 link between the primitive oxidizing bac- 

 teria and the Peritrichinas. They include 

 the fluorescent water bacteria and the phos- 

 phorescent vibrios and at the higher end of 

 the series such forms a.s the cholera organ- 

 ism in which the ability to split complex 

 products with the formation of lactic acid 

 and indol begins to appear. 



The second order, the Peritrichinse, in- 

 cludes the more specialized bacteria in 

 whose metabolism the splitting of carbohy- 

 drates or amino-acids plays a primary role 

 rather than oxidation or denitrification. 

 They are rods or cocci, peritrichous when 

 possessing flagella at all, and among them 

 are found all the commoner putrefactive 

 and parasitic types. This order, according 



