IVAN C. HALL 209 



of anaerobes by Larson, Cantwell, and Hartzell' in broth whose surface tension has 

 been reduced by castor-oil soap. 



The really important point concerned in the attempts to "aerobize the anaerobes" 

 involves the fundamental validity of differentiating micro-organisms according to 

 their oxygen relation and the stability of this relation. 



There have been a few efforts to "aerobize the anaerobes" by acclimation to in- 

 creasing oxygen tensions. Ferran' claimed that by starting with pure acetylene and, 

 as growth began, mixing more and more air, he could accustom the tetanus bacillus 

 to growth in air on the surface of broth without morphological change. But the 

 formation of a thick pellicle and loss of virulence reported is suggestive of aerobic 

 contamination, for the detection of which no special procedures appear to have 

 merited description in his brief publication. But even if surface growth of a pure 

 culture of tetanus bacillus did occur on the surface of liquid media in a flask, and the 

 writer has seen this without loss of toxicity, it could not be considered correctly as 

 aerobic in view of the swe^ing out of oxygen from liquid cultures by other gases 

 evolved; Ferran's claim fails to meet the requirements of our definition of aerobic 

 growth. 



The progressive transformation of strict anaerobes into aerobic micro-organisms 

 has received extended attention by Rosenthal,' who held that the distinction between 

 aerobes and anaerobes is not fundamental. By successive cultivation in tubes con- 

 taining milk of less and less depth or covered with thin layers of lanolin, Rosenthal 

 claimed to have cultivated the anaerobic bacilli of botulism, Achalme {B. welchii), 

 and Legros, under conditions of partial exposure to air, which had hitherto failed to 

 permit growth. No surface colonies on solid media were secured at this time, but 

 later surface colonies were obtained with difficulty with the bacillus of Achalme by 

 more persistently decreasing the depth of milk. Partial evacuation was also used but 

 with somewhat incomplete success. Similar experiments were conducted with Vi- 

 brion septiqiie, and Rosenthal soon came to believe that there were three steps in the 

 transformation of anaerobes into aerobes as follows: 



First, the organisms lost their oxygen intolerance without alteration of biochemi- 

 cal functions (e.g., fermentation, putrefaction) or of biological properties (e.g., vir- 

 ulence). Such cultures were said to grow for one generation only upon the surface of 

 solid media in pure culture and when transferred to deep media displayed immediately 

 their usual characteristics. Repeated transfers in this stage upon solid media were 

 impossible. 



Second, after the second or third agar slant the organisms lost their identifying 

 biochemical characteristics, but these might be restored in a few generations by re- 

 peated transplantation in suitable media under anaerobic conditions. 



Third, cultures lost their identifying chemical properties as well as their patho- 

 genicity permanently, though they were morphologically unchanged. 



Reaching the foregoing conclusions in experiments with the bacillus of Achalme, 



• Larson, W. P., Cantwell, W. F., and Hartzell, T. B.: J. Infect. Dis., 25, 41. 1919. 



^ Ferran, J.: Cenlralbl.f. Bakteriol., Abt. I, Orig., 24, 28. 1898. 



3 Rosenthal, G.: Compt. rend. Soc. de biol., 55, 1292. 1903; 60, 828, 874, 928, 957, 1116. 1906; 

 61, 48, 211, 326, 440. 1906; 62, 438, 578, 784, 1020, 1066, 1119. 1907; 64, 398. 1908. 



