14 THE BACTERIOPHAGE AND ITS BEHAVIOR 



that the action is more rapid and complete with vigorous-growing young cultures 

 than with old ones, and there is very little action on dead cultures or on young 

 cultures that have been killed by heating at 60°C. Anaerobia does not favor the 

 action. The transparent material when diluted (one in a million) with water or 

 saline was found to pass the finest porcelain filters (Pasteur-Chamberland F. and 

 B. and Doulton White) with ease, and one drop of the filtrate pipetted over an 

 agar tube was sufficient to make that tube unsuitable for the growth of the micro- 

 coccus. That is, if the micrococcus was inoculated down the tube as a streak, 

 this would start to grow, but would soon become dotted with transparent points 

 which would rapidly extend over the whole growth. The number of points from 

 which this starts depends upon the dilution of the transparent material, and in 

 some cases it is so active that the growth is stopped and turned transparent al- 

 most directly it starts. This condition or disease of the micrococcus when trans- 

 mitted to pure cultures of the micrococcus can be conveyed to fresh cultures for 

 an indefinite number of generations; but the transparent material will not grow 

 by itself on any medium. If in an infected tube small areas of micrococci are 

 left, and this usually happens when the micrococcus has grown well before be- 

 coming infected, these areas will start to grow again and extend over the trans- 

 parent portions, which shows that the action of the transparent material is 

 stopped or hindered in an overgrown tube; but it is not dead, for if a minute 

 portion is transferred to another young culture of the micrococcus it soon starts 

 to dissolve up the micrococci again. Although the transparent material shows no 

 evidence of growth when placed on a fresh agar tube without micrococci it will 

 retain its powers of activity for over six months. It also retains its activity when 

 made into an emulsion and heated to 52°C., but when heated to 60°C. for an hour 

 it appears to be destroyed. It has some action, but very much less, on Staphy- 

 lococcus aureus and albus isolated from boils of man, and it appears to have no 

 action on members of the coli group or on streptococci, tubercle bacilli, yeasts, 

 etc. 



Such is the description given by Twort of the phenomenon which 

 he observed. 



The first remark, extremely important, is that there is no lysis, no 

 dissolution of the bacteria. The final result of the transformation as 

 described by Twort is a vitreous or transparent substance, formed of 

 fine granules which take a red tint when stained with Giemsa. There 

 is a fragmentation of the cocci, a phenomenon of bacterioclysis. 



In the phenomenon of bacteriophagy a complete dissolution of the 

 bacterial cell takes place. There is no residue. 



But since Twort says nothing in any of his papers, neither in that 

 of December, 1915, nor in that of 1922^°^ of what happens when he 

 adds his "transparent material" to a broth suspension of staphylococci, 

 it is not possible to establish a comparison. It is necessary, there- 

 fore, to restrict our comparison to the characteristics of the two phe- 

 nomena as manifested on agar. 



