THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 341 
about under the circumstances referred to, it occurred to M. 
Pasteur that it might perhaps be the oxygen of the air 
admitted to the vessels. Oxygen is essential to the growth 
of the organism, but it might, as M. Pasteur thought, be, 
nevertheless, in long-continued action upon it, a cause of 
weakness. With a view of testing this idea he instituted culti- 
vations of the bacterium in broth contained in tubes partially 
filled with the liquid, that is to say, containing a certain 
proportion of their volume of air, but sealed hermetically. 
The result was a growth of the organism, indicated by tur- 
bidity of the clear fluid, attaining a degree proportioned to 
the amount of air present in the tube, but soon coming 
to an end when that air was exhausted, so that the little 
organism, no longer growing throughout the liquid, fell to 
the bottom of the vessel, leaving the fluid again clear. The 
organism having now exhausted all the free oxygen, was 
from this time forth presumably protected from the influence 
of that element, and, in exact accordance with M. Pasteur’s 
theory, it was found that no matter how long these closed 
tubes were kept, the organism retained not only its vitality, 
but its full virulence, as tested by inoculation of healthy 
chickens.! 
These facts are certainly fraught with the deepest interest, 
and the medical world must for ever remain deeply indebted 
to M. Pasteur for eliciting them. Doubts may, however, be 
entertained regarding the interpretation of the phenomena. 
Thus Dr. Greenfield, whose own researches have had special 
reference to the modifying influence exerted upon bacteria 
by the medium in which they grow, has thrown out the 
suggestion that the enfeeblement of the organisms of fowl 
cholera grown with free access of air may be due to altera- 
tions in the fluid which they inhabit rather than to the 
effect of oxygen upon them. When free access of oxygen is 
permitted, the organism, he contends, will continue to grow 
till all the material suitable for its nutrition is exhausted, 
and as the nutriment becomes defective the progeny will be 
feeble. At the same time this exhaustive development of 
the organism will be attended by the full measure of possible 
alteration in the quality of the liquid which the growth of 
the organism can effect, and this alteration will naturally 
involve the production of substances which may exert a 
prejudical influence upon the organism itself. On the other 
hand, the bacterium, when growing in a sealed tube with 
limited supply of oxygen, has its development brought to a 
stand by the exhaustion of that gas, while the organism is 
1 See ‘Comptes Rendus,’ 26th Oct., 1880. 
