188 TEXT-BOOK OF BACTERIOLOGY. 



in this case light is developed; and that this development of light 

 is nevertheless only functional, as, for example, contraction is func- 

 tional in the muscles, which always produce heat and COa; that 

 under certain conditions (absence of oxygen") the phosphorescence 

 can cease without any interruption to the growth of the bacteria, 

 will be for future investigators to determine. 

 None of the glow bacteria possess pathogenic qualities. 



Bacterium Termo. 



If we examine a putrid solution of organic matter in a stained 

 preparation or in a hanging drop, we find a surprisingly large 

 number of micro-organisms, and we already know that putrefac- 

 tion only takes place in consequence of bacterial action. In partic- 

 ular we will almost always find certain very mobile rod-cells of 

 moderate size, which certainly stand in a very intimate relation to 

 the decomposition of substances containing albumin. 



Of what species are the bacilli which seem destined to perform 

 such an important part in so essential a process ? 



As long as the microscope was the only means of gaining an 

 insight into bacterial life, all these micro-organisms were considered 

 as belonging to one single species, to which the name Bacterium 

 termo was given. The name was given bj' Dujardin and Ehren- 

 berg, and a precise description was supplied hj F. Cohn. 



According to the latter, the Bac. termo occurs in the form of 

 rod-like cells, twice or three times as long as they are broad, often 

 united in pairs, but rarelj^ in long rows, and with lively powers of 

 locomotion. In Cohn's nutritive solution, the composition of which 

 has been given, they thrive very luxuriantly, the liquid becomes 

 turbid, and a greenish, iridescent scum forms on its surface. 



This is certainly a pretty full description, which satisfied the 

 demands of bacteriological science so completelj' that Cohn himself 

 regarded this species as clearly characteristic and well defined, 

 calling it the "ferment of putrefaction, without which the latter 

 could neither begin nor continue," and attributing to it an office of 

 the very highest importance in the economy of nature. 



But such conclusions cannot stand before the requirements of 

 more recent times. They want precisely that proof which at the 

 present day every bacteriological fact must be able to show. They 

 have not passed the ordeal of pure culture and the application of 

 modern methods of examination. 



If these methods be employed upon the material which is found 

 in the observation of putrefaction, the single Bacterium termo re- 



