70 BIOLOGY AND TECHNIQUE 



would gradually spread over the whole group. Such action was 

 complete and rapid only with vigorously growing young cultures, 

 but had little effect on dead cultures. The action took place best 

 under aerobic conditions. If the transparent material was diluted 

 and filtered and then added to an agar slant of similar organisms, 

 growth was prevented. The transparent material did not grow on 

 any medium and was destroyed in its activity at 60. Its action 

 on staphylococci grown from boils was very slight, and there was 

 no action of the substance upon B. coli, streptococci, tubercle bacilli 

 or yeasts. The nature of the material was left undecided by Twort. 

 It was supposed that it might be a parasitic organism which de- 

 stroyed the bacteria, perhaps an amoeba, but he thought that it 

 was probably a substance derived from the bacteria themselves, 

 since it occasionally reappeared in glassy cultures months after sub- 

 culture. Twort investigated this peculiar occurrence not only with 

 vaccine virus, but also with Gram-negative bacilli obtained from 

 the intestines of a dog suffering from acute distemper and some 

 organisms derived from infantile diarrhea. 



In 1917 D'Herelle 35 began the publication of a series of notes 

 upon a phenomenon unmistakably identical with that of Twort. 

 When he introduced two or three drops of a dysentery stool into 

 about 20 c.c. of broth and filtered this through a Chamberland 

 Candle and introduced a trace of this filtrate into a young Shiga 

 bacillus culture, it caused a clearing up of the culture within a 

 few hours, transplants remaining sterile. A trace of this dissolved 

 culture placed into another young broth culture of dysentery 

 brought the same result, and in this way he made 935 successive 

 passages of the lytic principle. His technique in detail was as fol- 

 lows : He made an emulsion of fecal material and filtered it through 

 a filter candle. With a pipette he then transferred 1 c.c. of this 

 filtrate into a small tube and inoculated this material with a drop 

 of a young dysentery or typhoid culture. This tube is held for 

 from 12 to 24 hours at a temperature of 22, and is then placed 

 for 2 or 3 hours at 37. If the stool filtrate contains a lytic prin- 

 ciple, the inoculated tube will be transparent at the end of this 

 time, and the lytic principle can be transmitted in series from this 

 tube. He assumed from his ability to keep this lytic activity going 



33 D 'Herelle, Compt. Kend, de la Soc. Biol., 81, 1918, 1160, 82, 1919, 1237, 83, 

 1920, 52, 97 and 247. 



