i8 95 . NOTES AND COMMENTS. . 223 



Artificial Production of Varieties of Bacteria. 



The power of reproduction by forming spores is one of the first 

 qualities of bacteria to rise in the mind. The habit of the filaments, 

 to break up into spores when conditions are unfavourable to growth, 

 the resisting powers of spores and the ease with which they spread 

 from place to place, would seem properties inevitable in bacteria. 

 The power of spore-formation, however fundamental we may have 

 thought it, apparently can be altered by environment at the will of 

 the experimenter. 



In the December number of the Annales de ITnstitut Pasteur, 

 MM. Surmont and Arnould publish the results of some very striking 

 investigations upon the bacillus of anthrax. They set out from the 

 remarkable but somewhat neglected experiments of Chamberland and 

 Roux, who, in 1883, succeeded in creating a race of bacteria that had 

 definitely lost the power of spore-formation. A number of in- 

 dependent investigators from time to time have obtained similar 

 results, but their methods were so varied and their results so uncertain 

 that the present authors resolved definitely to investigate the whole 

 question. They tried a number of different methods, but came to the 

 conclusion that the use of carbolic acid was the most successful. 

 The bacilli of anthrax cultivated in veal-broth which contained a 

 trace of carbolic, rapidly turned into a variety devoid of the power of 

 spore-formation. The filaments remained unbroken, or, brought into 

 conditions usually favourable to spore-formation, simply decayed. 

 But there is a remarkable difference between colonies of the bacilli 

 from different sources. Some from a very virulent source continued 

 sporogenic after the carbolic treatment ; other and less virulent 

 colonies rapidly lost the power of spore-formation. Extended experi- 

 ments showed, however, that there was no direct connection between 

 the degree of attenuation and the susceptibility to the influence of the 

 carbolic acid. Their conclusion was no more definite than that 

 " certain races of Bacillus anthracis are very difficult to transform into 

 asporogenic forms." But the interesting result was obtained that 

 such obdurate races yielded after they had been cultivated for some 

 time at a temperature of 42 . Taking an obdurate race, they grew 

 from it a long series of cultures at that temperature, and the race 

 produced at the end of the series rapidly became asporogenic under 

 the carbolic treatment. 



To the specialist in Bacteriology these experiments will have 

 peculiar value, and as the spore-producing power is a chief danger in 

 the bacteria of disease, as it is the chief agency by which the diseases 

 survive and spread, the transformation of bacteria into sterile races 

 may have an important bearing on public health. But to the 

 biologist the experiments come with a wider meaning. What we 

 want just now is exact investigation into the limits and the extent of 

 plasticity in living things. How far do surrounding things mould a 

 living organism ? Here is a case where the method of reproduction 



