Aug. 19, 1922] SECTION OF MICROBIOLOGY. [ MEorcAL jL"rnal 



the mere striking of a match, it can be indefinitely reproduced if fuel is pro- 

 vided. A still more striking, because more biological, example is found in blood 

 coagulation. Suppose a series of tests tubes containing a stable plasma— bird's 

 plasma, for instance— which will remain indefinitely fluid. To the first tube 

 we add just a few cubic centimetres of distilled water. As a result of that 

 initial thromboplastic action, which does not need to be repeated to the future, 

 thrombin suddenly appears in the first tube and the plasma clots. If a few 

 drops of the exudate serum in the first tube are pipetted off and poured in the 

 next tube, this second tube clots, in its turn, with a new regeneration of throm- 

 bin, which, transferred in the third tube, brings about the coagulation of that 

 tube with again a new production of thrombin, and so on indefinitely. In this 

 way we realize the transmissible coagulation of blood in series, with the con- 

 tinuous regeneration of thrombin, and thrombin is not a living being. 



The localization of the lytic action of diluted bacteriophage can be 

 explained by the hypothesis of a chemical substance as well. It must be kept 

 in mind that a culture is not a homogeneous whole, but made up of organisms 

 showing all kinds of qualitative and quantitative individual differences— that 

 is, as far as their susceptibility to the lytic agent is concerned. When a very 

 concentrated lytic agent is poured over the surface of an agar culture an almost 

 complete dissolution occurs, with the exception of just a few organisms 

 resistant enough to overwhelm the strong action of the concentrated lytic 

 agent. On the other hand, when a diluted lytic agent is used only the few 

 extremely sensitive bacteria will be influenced, and each of them becomes a 

 centre of regeneration of the lytic agent, which, diffusing evenly in every 

 direction, produces perfectly round spots of clarification very often surrounded 

 by a kind of halo of diffusion. Between these two extreme conditions all kinds 

 of intermediate degrees exist. Further, any substance, living or not, is com- 

 posed of particles, molecules, atoms, or ions. When we pour out a glass of 

 soda water, there appear on the wall of the glass small round bubbles of gas, 

 the size of which increases exactly as the so-called colonies of bacteriophage, 

 and yet gas is not a virus. 



3. The idea of the bacteriophage being a product of bacterial activity is 

 suggested by the close parallelism existing between the regeneration of the 

 lytic agent on the one hand, and the activity of growth of the bacteria on the 

 other hand. 



No regeneration ever occurs in dead cultures, nor in living cultures when 

 put in such conditions that they cannot grow— in saline emulsions of bacteria, 

 for instance, or at low temperature. A slight lysis, with but a small regeneration 

 of lytic agent, is induced in the slow-growing culture of B. coli in a svn- 

 thetic medium. On the contrary, an abundant regeneration occurs in a fast- 

 growing culture in broth. A recently seeded broth culture to which is added 

 just a trace of lytic agent will not be inhibited; but a few hours later, at the 

 very moment the culture reaches its acme of growth, a rapid dissolution 

 occurs with an abundant regeneration of lytic agent. 



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