CHEMICAL CRITERIA OF ANAEROBIOSIS 29 



I have noted elsewhere (1915) that, culturally, the growth of 

 obligative anaerobes is delayed under oil except where relatively 

 large inocula are used. In certain experiments, comparing the 

 efficacy of the marble and oil (2.5 cm.) seals in constricted tubes 

 with identical media, growth has been negative with the oil 

 seal in twenty-four to forty-eight hours at a million times the 

 dosage showing definite growth under the marble. Continued 

 observation of the oil tubes has usually decreased the dispro- 

 portion, however. Although these experiments suggest an 

 inhibitive action of the oil this was not substantiated by com- 

 paring progressively diluted cultures under both the oil and 

 marble wdth a similar set under the marble only; in this case 

 equivalent dilutions developed in parallel order. 



In this connection it was interesting to study the effect of 

 filling a constricted tube with alkaUne methylene blue solution 

 and oil in such a way that the marble seal lay in the oil. The 

 results of a carefully controlled experiment are summarized 

 herewith, the solutions having been decolorized first in the usual 

 way by heating and removed for observation. 



Ten minutes 



Tube 1 — No seal Solution blue 



fBlue above 

 Tube 2 — Marble in solution <{ Colorless below — remained so 



[ for over two weeks. 



Tube 3 — Marble in oil Solution blue 



Tube 4 — Oil alone Solution blue 



Tube 3 in addition to showing this remarkable result also 

 shows regularly, in such an experiment, a striking and fakly 

 permanent emulsification of water in oil which has been made the 

 subject of a special monograph by the writer (1917). 



But it was most disconcerting to find that the marble placed 

 in the oil fails to protect the decolorized solution from recolor- 

 ation on cooling and suggests that the effect of heating a solution 

 in contact with oil is to drive the oxygen from the solution in 

 which it is less soluble, into and possibly to some extent through 

 the oil, in which it is more soluble, and that on cooling there is 

 a return of some of the oxygen from the oil to the solution. 



