THE MECHANISM OF BACTERIOPHAGY 113 



5ju, and between the normal forms and the spherical forms are to be 

 found all intermediates. But despite this variable morphology all 

 of the cells have a sharply outlined contour. 



If the spherical cells are observed with care it is seen that after a 

 variable length of time, sometimes amounting to only about 10 minutes, 

 an actual bursting takes place; a process consuming only a fraction of 

 a second. Immediately afterward, in the place of the spherical cell 

 there remains a slightly cloudy floccule which slowly dissolves. These 

 spherical cells are particularly abundant at the time when the dis- 

 solving process is at its maximum rate. There can be no question 

 concerning the nature of these cells; they are bacilli which, operated 

 upon by a force exerting its effects from within, take at first a globoid 

 form and later rupture. This is the more certain since at times one 

 can witness the rupture of the swollen bacilh, even before they have 

 assumed a completely spherical contour. This observation provides 

 direct proof that the corpuscle develops and exerts its action within the 

 bacterial cell. Destruction of the bacilh would be an entirely dif- 

 ferent process if the dissolving action were exerted on the exterior. 

 The spherical form and the bursting process prove beyond doubt that 

 the operating force is internal (d'Herelle^^^* ^23^* 



Although, as stated above, it is best to make microscopic observa- 

 tions with a suspension in the process of being dissolved under the 

 action of a poiverful bacteriophage, this does not mean that the 

 rupture of the bacterial cell takes place in this case only, for the phe- 

 nomenon has occurred in the same manner with all of the races of the 

 bacteriophage which I have isolated. It is, however, more readily 

 observed when bacteriophagy is intense. I am convinced, because 

 of various experiments with bacteria of varied species and with bac- 

 teriophage races of different types, that the destruction and the dissolu- 

 tion of the bacteria occurs always by bursting. But in the case of 

 a slightly active bacteriophage the process may pass unobserved, for 

 the number of ruptures occurring at a given moment is then extremely 

 small, and it is pure "chance" if the rupture of a cell takes place at a 

 given time within the extremely minute quantity of material under 

 the objective of the microscope. With such materials it may at times 



* The bursting phenomenon was first observed by P. Jeantet, Chief of the 

 Laboratory of Microphotography at the Pasteur Institute. There are few who 

 have the capacity for microscopic observation as highly developed as he. More- 

 over, he has the habit, as rare as it is original, of not publishing the things which 

 he observes. Instead of taking to himself the credit for those things disclosed in 

 the studies in which he takes an interest, there are many who have benefited 

 from his powers of observation. 



