BACTERIOLYSIS 25 



The active bacteriophage may be sought for in materials which 

 require some preliminary treatment, since in their natural physi- 

 cal state they may not lend themselves readily to nitration. 

 The following types of material may be examined as a source 

 of the bacteriophage. 



1. A sterile fluid; sterile in the sense in which the word 1 is 

 usually employed; for example, blood, or an organic fluid col- 

 lected aseptically. With such no treatment is necessary. 



2. The material to be examined may be a clear liquid but not 

 sterile. With this, filtration will eliminate the bacteria while 

 the bacteriophage passes through into the filtrate. 



3. The material may show a homogeneous turbidity; as a 

 bacterial culture. Here, direct filtration results in an early occlu- 

 sion of the pores of the bougie. Thus, it is desirable to resort to 

 a preliminary filtration. The following method of treatment 

 is most satisfactory. 



Provide a funnel with a folded filter paper sufficiently large to receive 

 at one time the entire volume to be filtered. Fill the filter with water to 

 which has been added a small amount of infusorial earth. When the water 

 has passed through, the paper is left coated with a thin layer of the infuso- 

 rial earth, thus rendering the paper less permeable. Through this the 

 material to be examined is filtered prior to filtration through the bougie. 



4. The material may be a fluid holding in suspension organic 

 particles, or it may be matter more or less solid in nature. This 

 is the type of substance most frequently examined; such as fecal 



1 In the course of this work I find myself frequently in difficulty in the 

 exposition of facts because of certain expressions which have been appro- 

 priated to describe certain conditions. I shall apply the word sterile to 

 a medium which contains no visible microscopic organisms or organisms 

 capable of cultivation upon artificial media. An ultrasterile medium is 

 one which contains no ultramicrobes. A substance containing the virus of 

 measles, for example, is sterile but not ultrasterile, since it is still capable 

 of transmitting measles although it contains nothing visible or cultivable. 

 Media containing the bacteriophage are likewise sterile in the bacteriologi- 

 cal sense of the word, since they are perfectly limpid and since the germ 

 which they contain can not be cultivated alone upon artificial media of any 

 kind. But such a medium is not ultrasterile, for it does contain a principle 

 which will grow at the expense of bacteria, just as the virus of measles will 

 grow at the expense of higher organisms. 



