256 PASTEUR: THE HISTORY OF A MIND 



of a bird, drawn from the animal, is an excellent culture 

 medium for the bacteridium. Why does it resist in- 

 fection in the animal? Because "the living blood in 

 full circulation is filled with an infinite number of cor- 

 puscles which in order to live and perform their physio- 

 logical function, need free oxygen: it might be said that 

 the blood corpuscles are obligate aerobes. When, there- 

 fore, the anthrax bacteridium, enters normal blood, 

 it meets there an enormous number of organic indi- 

 vidualities ready, figuratively speaking, for what one 

 sometimes calls the struggle for existence, ready, in 

 other words, to seize for their own use the oxygen nec- 

 essary for the existence of the bacteridium." 1 



We see developed here the formula and the ideas of 

 Darwin, but in a singularly precise form. What could 

 be more vague than the phrase "struggle for existence?" 

 But "struggle for oxygen," that opens the way to ex- 

 perimentation, and Pasteur begins at once. 



Some common bacteria sown with the anthrax bacter- 

 idium, in neutral or alkaline urine, prevent its developing 

 because they take possession of the ground more rapidly 

 and exhaust the oxygen. They can, in the same way, 

 arrest its development in an animal. "It is possible 

 to inject great quantities of the anthrax bacteridium 

 into an animal without its contracting the disease, if 

 some of these common bacteria have been present in 

 the culture used." Here we have the first example of 

 bacteriotherapy, to which Cantani returned later, and 

 which has not spoken its last word. 



The interpretation of these facts has changed, and 

 we know now that it is less simple [than it seemed at that 

 time] but the idea of the struggle for existence was never- 

 theless then introduced into pathology, in the domain 

 of cellular antagonism : and it has remained there. 



1 Comptes rendus de 1'Academie des Sciences, 16 juillet, 1877. 



