114 THE BACTERIOPHAGE 



per cubic centimeter 



Before centrifugation 1,750,000,000 



;.. .. /Surface 50,000,000 



After centnfugation| Bottom 3,700,000,000 



Dialysis through collodion membranes of various permeabilities 

 gives a rough approximation of the size of the bacteriophagous 

 ultramicrobe. As a test, one part of horse serum was mixed with 

 three parts of a culture of the bacteriophage, and the mixture was 

 subjected to dialysis. Whenever the albumin passed through the 

 filter the bacteriophage passed also, and when the permeability 

 was such that the albumin was held back, so also was the bac- 

 teriophage. 



The bacteriophage then, passes through when the molecule of 

 serum albumin passes and is retained when the latter is held back. 

 It remains for physicists to more exactly determine its true size, 

 and this determination will be of more interest since the bac- 

 teriophage is the only ultramicrobe with which such measurement 

 is actually possible, since it is the only one where the elements 

 can be counted. Thus, it may serve to clear up an important 

 point touching the constitution of organized matter. If one 

 calculates the ultramicrobe as being one one-hundredth of a 

 micron in diameter, it ought to contain about twenty molecules 

 of albumin and five or six atoms of sulfur. Physicists have de- 

 termined the size of the pores in the most dense collodion mem- 

 branes as being not greater than two millionths of a micron. But 

 the ultramicrobe of avian plague penetrates such a membrane. 

 Each element can not be greater than one five-thousandth of a 

 micron in diameter, hence it would be composed of one-tenth of 

 a molecule of albumin. On the other hand, an ultramicrobe is 

 indeed a markedly complex organism, capable of adaptation, 

 possessing the faculty of secreting toxins, — the diastases, — having 

 in a word, the characteristics of living matter. This in itself 

 implies a relatively complex organism. We find ourselves, then, 

 cornered by an absurdity, for it is impossible to conceive of a 

 complex organism formed of a single molecule, much less of the 

 tenth part of one. It will be much more simple to admit that it 

 is impossible to understand under what aspect life is present in 

 the ultramicrobe and under what form the matter composing it 

 exists. 



