INTRODUCTION 21 



TECHNICAL PROCEDURES* 



Every bacteriological laboratory possesses the materials necessary 

 to conduct experiments upon bacteriophagy. I will only mention the 

 apparatus needful for the isolation of the bacteriophage but I believe 

 it pertinent to discuss the procedures usually employed in biology to 

 effect filtration.f 



Under ordinary circumstances the bacteriophage passes through all 

 of the usual filter candles, including those made of porcelain, of in- 

 fusorial earth, of asbestos, etc. Thus, it is possible to use candles of 

 all types, but simply because of economy, in view of the large number 

 of filtrations which it is necessary to make, it is preferable to employ 

 candles which can be sterihzed and repeatedly used. Chamberland 

 filters are of this type. A small candle, with an outside length of 7 to 

 8 cm. may be obtained, which is particularly convenient for test 

 filtrations carried out with small quantities of fluid. It is thus possible 

 to filter the contents of a tube of bouillon containing about 10 cc. and 

 to recover 7 to 8 cc. of filtrate. 



Immediately after the filtration is completed, before the liquid 

 saturating the filter has dried, I would suggest that the filter be boiled 

 in water, as in a casserole, a procedure which is adequate to kill the 

 pathogenic organisms which were present in the fluid subjected to 

 filtration (in the case of spore-producing pathogens it is obviously 

 necessary to subject the filters to autoclaving at 120°C.). After boiling 

 for about 10 minutes the candles can be removed from the boihng water 

 with forceps and placed in the incubator at 37°C. to dry. When a 

 number of used filters have been collected they can be sterihzed by 

 heat, care being taken that the temperature does not go sufficiently 

 high to damage the material (as the enamel) of which the filter is made. 

 The small amounts of organic material present in the filters after 

 boiling, provided the boihng process is carried out before the filters 

 dry after the filtration, are thus consumed and the filter is restored to 

 a condition comparable to a new candle. By proceeding in this 

 manner it is possible to work for several years, carrying out from 6 to 

 8 filtrations daily, with 4 or 5 dozen filters, without having to supple- 

 ment the supply. I emphasize this question a Httle because a number 



* This section of the text is of interest only to those engaged in experimental 

 work upon the subject of bacteriophagy. 



t On this subject, of such extreme importance from the point of view of the 

 study of all ultraviruses, consult the text already mentioned — Immunity in 

 Natural Infectious Disease. 



