INTRODUCTION 19 



discussion. Dangeard* has described a Chitridinea, belonging to the 

 group of Oomycetes, which parasitizes and develops in the nucleus 

 of Ameba verrucosa Ehr. He has termed this Nucleophaga amebae. 

 The word "phage" has exactly the same meaning in the two cases. 



Up to the present time we have considered the term "sterile" as 

 implying the freedom of a medium from visible or cultivable bacteria. 

 Nevertheless a medium termed "sterile" is contaminated if it contains 

 an ultravirus, whether this virus be the bacteriophage or the virus of 

 rabies, of vaccinia, or of avian plague, even though the highest magni- 

 fications of the microscope fail to reveal the living agent or our arti- 

 ficial media fail to yield a growth. For it is only necessary to place 

 this material in contact with a susceptible Hving being to demonstrate 

 that "a something" is present which can be cultivated in vivo. Con- 

 sequently, although such a medium is termed "sterile" it is not so in 

 reality. In the discussion to follow the term "sterile" will be em- 

 ployed in its usual sense, and we will designate as "ultrasterile" a 

 medium which contains neither visible microorganisms nor an actually 

 demonstrable ultravirus. I underscore the word actually for it is quite 

 possible that we may sometime discover that there is no organic 

 medium, natural or artificial, which is ultrasterile, at least, until after 

 it has been subjected to an adequate amount of heat or treated with 

 appropriate antiseptics. Only thoSe ultraviruses which exercise a 

 definite pathogenic effect upon another living being are demonstrable 

 at the present time. Among the saprophytes only those can be de- 

 tected which produce a demonstrable chemical transformation.! 



When one introduces a trace of bacterial culture into or upon a 

 medium one says that this medium is "inoculated." Evidently the 

 same word might be employed to designate the introduction of a trace 

 of liquid containing the bacteriophage into a medium. It would be 

 necessary to say "I inoculate bouillon with such and such a bacterium 

 and again inoculate it with the bacteriophage," and such a statement 

 in certain cases at least could readily lead to confusion. I shaU employ 

 then, the term "inoculate" in its usual sense, meaning the introduction 

 of a bacteriophage into a medium, and when bacteria are introduced 

 into a medium the terms used will be "plant," "implant," or "seed." 

 Thus, I may say "I implant a medium with such and such a bacterium 

 and then "inoculate" it with the bacteriophage." 



* Dangeard, P. A— Le Botaniste, 1894/95, No. 4, 199; 248. 

 t With reference to this subject see Immunity in Natural Infectious Disease, 

 Williams & Wilkins Co., Baltimore, 1924. 



