230 THE BACTERIOPHAGE AND ITS BEHAVIOR 



well developed fermentative power producing gas but they do not give indol and 

 do not change the color of litmus lactose agar. After a few transplants one 

 finds either a return to the typical reactions or a persistence of the abnormal 

 characters. The sugar fermentation reactions can be observed only by im- 

 planting the sediment into sugar-containing agar and it sometimes requires 

 three or four days for the fermentation to reach its maximum. 



The morphological characters of the elements which form secondary cultures 

 after filtration may persist throughout a series of transplants. The elements 

 are comparable to those which have been described above: isolated granules, 

 masses supported on a network, occasional bacilli, etc. In certain cases there is 

 a return to the bacillary form. 



To summarize all this, the granules described by Hauduroy are 

 certainly the coccus forms such as I have observed in a simple secondary 

 culture and of which I have spoken in preceding paragraphs. It is, in 

 fact, certain that in ordinary secondary cultures obtained after complete 

 bacteriophagy, the formation of ultrabacteria takes place in the same 

 manner as in the filtrates. It is even probable that all secondary cul- 

 tures developing after a complete bacteriophagy with a total clearing 

 of the medium result from the formation of ultrabacteria which then 

 reproduce in the form of cocci and later pass into the normal form. 



In reality, what are these ultrabacteria? In the second part of this 

 text I will give the hypothesis which I have formed^^^ and which seems 

 to me to be the only one to accord with the facts. At the moment I 

 will only state that I have shown these filterable bacterial forms to be 

 ultra-filterable, that is, they pass through collodion filters^^^ provided 

 the pores are sufficiently open to allow the serum albumin micella to 

 pass. Their dimension is, therefore, that of a protein micella. This 

 renders it apparent that the filterable forms of bacteria which de- 

 velop through the influence of the bacteriophage are in reality ultra- 

 viruses of the same size as those of variola, of encephalitis lethargica, or 

 of rabies. We will see later the importance of the fact that there are 

 ultrabacteria, 



12. NATURAL MIXED CULTURES 



Bacteriophagy is a phenomenon occurring under natural conditions. 

 We will see that the bacteriophage is a normal inhabitant of the intes- 

 tinal tract throughout the animal series from the insects up through 

 man. It is found in everything which is exposed to contamination by 

 excreta; in the water of rivers and of the sea, in the soil and in the dust. 

 Within the animal it does not remain confined to the intestine but it 

 may pass into the circulation and through this channel it may be con- 



