EELATION OF PATHOGENIC TO SEPTIC BACTERIA. 27 



cultivation just described. It must be borne in mind that for 

 the success of this method it is imperative, in a greater degree 

 than in the other previously mentioned methods, that the 

 cotton-wool plug is thoroughly sterilised. For it is obvious 

 that if this is not the case, by the piercing of the cotton-wool 

 plug with the capillary pipette wool fibres are always carried 

 down into the nourishing material, and if these are not 

 thoroughly sterilised a contamination of the latter must inevit- 

 ably follow. 



I had charged twelve test-tubes with pork broth, and had 

 them well plugged with cotton wool, well boiled on two suc- 

 cessive days, and placed into the incubator at 32° — 35° C. ; 

 they were kept here for two weeks, and remained perfectly 

 limpid and sterile. I then inoculated six of them in the above 

 manner with Bacillus anthracis of an artificial cultivation, 

 viz. introducing the bacilli by piercing the capillary tube con- 

 taining them through the cotton-wool plug. After twenty- 

 four hours all showed signs of accidental contamination. I 

 remembered that I had kept the test-tubes for several hours, 

 and at two successive days, at 140° — 150° C. ; but the cotton 

 wool had been tightly compressed in a beaker, and exposed only 

 for about an hour to a temperature of about 120° C. From the 

 remaining six test-tubes I removed the plugs of this cotton 

 wool, and closed them with fresh plugs of thoroughly sterilised 

 cotton wool. They were well boiled and kept in the incubator 

 for several days; as they remained quite limpid they were 

 inoculated after the same maner and with the Bacillus 

 anthracis of the same cultivation as in the case of the first 

 six test-tubes; the result was completely satisfactory; no 

 accidental contamination occurred. From this it is clear that 

 the test-tubes and the nourishing material were sterile in both 

 instances, and also the bacillus to be sown was the same, and 

 in a pure state in both cases, but in the first the cotton wool 

 was at fault, hence the accidental contamination introduced 

 into the nourishing material. 



As a rule, in cases where the naked-eye appearances do not 

 and cannot give indications of the actual state of the cultiva- 



