278 RECEPTORS OF THE THIRD ORDER 



BACTERIOPHAGE. 



Twort^ in 1915 described certain cultures of a micrococcus 

 on agar slants which showed areas of transformation into 

 transparent glass^'-looking spots. For this apparent lysis 

 Twort proposed various explanations none of them satis- 

 factory even to himself. D'Herelle 1917 and since has re- 

 ported similar phenomena of the clearing of large or small 

 areas on surface growths and also the clearing of broth cul- 

 tures. This phenomenon has become known as the "Twort- 

 D'Herelle phenomenon." D'Herelle has pursued investiga- 

 tions along this line most extensively.- He finds this lytic 

 substance frequently present in the intestinal tract of man 

 and animals recovered from or immune to various infections. 

 It is not specific but acts on different kinds of bacteria, 

 usually more vigorously on some than on others. Some 

 strains are not affected. D'Herelle showed that a small por- 

 tion, a drop, of fluid containing the principle will bring about 

 solution of an entire broth culture; a drop from this will 

 dissolve a second; from this a drop will dissolve a third and 

 so on indefinitely. // appears to grow in the cultures along 

 with the bacteria. It will not grow on dead bacteria. D'Herelle 

 concludes that these phenomena are due to an imtramicro- 

 scopic parasite, a virus that grows only on living bacteria. He 

 has named this virus Bacteriophagum intestinale or bacterio- 

 phage. He is of the opinion that it plays a most important 

 part in recovery from many infectious diseases and in 

 immunity from them. As to the facts of lysis of bacteria as 

 described by D'Herelle there is no dispute. Numerous 

 workers have duplicated his results. Not all agree with him 

 in interpreting the phenomena as due to a living parasite of 

 bacteria or that the bacteriophage is of such importance in 

 immunity. The apparent growth of the "principle" might 

 be explained as due to continued production of it by the 

 growing bacteria. Final decision as to the nature of the 

 bacteriophage must await further research. 



1 "An Investigation of the Nature of Ultramicroscopic Viruses," Lancet, 

 1915, ii, 1241. 



2 The Bacteriophage by F. D'Herelle, English translation by George H. 

 Smith, 1922. Immunity in Natural Infectious Disease by F. D'Herelle, 

 English translation by George H. Smith, 1924. 



