BACTERIOPHAGY IN A FLUID MEDIUM 39 



Technic of isolation 



The isolation of the bacteriophage may be undertaken under one 

 or another of the following circumstances: 



1. The bacteriophage may be sought in a sterile fluid, for example, 

 in normal blood or in an organic fluid collected aseptically. With such 

 no treatment is necessary. 



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

 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 occlusion of the 

 pores of the filter candle. Thus, it is desirable to resort to a prelimi- 

 nary 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 

 infusorial earth, thus rendering the paper less permeable. Through 

 this the material to be examined is filtered prior to filtration through 

 the candle. 



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 material, more or 

 less fluid, pasty, or solid; or excreta admixed to a greater or less degree 

 with earth, organic debris, etc. In such a case it is necessary to dis- 

 integrate as completely as possible the material to be examined. 



To effect such a disintegration the most simple procedure consists 

 in carefully suspending the material in bouiUlon, about 5 grams to 50 cc. 

 of the medium, and incubating this suspension at 37°C. for from twelve 

 to eighteen hours. The bacterial fermentations which ensue, because 

 of the diverse organisms introduced into the medium, lead to a suffi- 

 cient disintegration. Upon removal from the incubator the material 

 may be treated, as indicated above, by filtration through infusorial 

 earth and a candle. 



If the material under examination contains the bacteriophage and 

 has been subjected to filtration, it will be found in the filtrate. 



We will see that the bacteriophage possesses an activity manifested 

 against a wide variety of bacterial species; without doubt against all. 

 We will also see that against a given bacterium this activity is very 



