RELATION OF PATHOGENIG TO SEPTIC BACTERIA. 23 



and to be transferred into the nourishing material contains no 

 other but the desired species. This is, however, not always a 

 simple matter. It is simple enough in the following cases : — 

 If I transfer to my nourishing material a droplet of blood taken 

 from the heart or the spleen of an animal just dead or dying of 

 anthrax, I am certain to have no other organism in the blood 

 except the Bacillus anthracis ; or if I have an artificial cul- 

 tivation of Bacillus anthracis which from certain definite 

 naked-eye appearances (see below), and still more from micro- 

 scopic examination of anilin-stained specimens, I can pro- 

 nounce with certainty to be a pure cultivation of Bacillus 

 anthracis, I shall be certain that I shall again, cseteris 

 paribus, obtain a pure cultivation, if sowing out from this 

 cultivation. Again, if I take an infusion of hay in which fer- 

 mentation produced by the hay bacillus has been completed — 

 that is to say, in which the bacillus has passed its whole cycle 

 and has yielded an abundant crop of spores forming a fi.ne brown 

 precipitate at the bottom of the infusion — and if I boil this in- 

 fusion for several minutes, I shall be sure to destroy everything 

 living except the spores of the hay bacillus, and if I sow out 

 from this so-boiled infusion I shall have the satisfaction to find 

 that the new growth contains only hay bacillus. 



The above modified use of Koch's method, viz, charging the 

 covering glass of the glass cell with a drop of liquefied gelatine 

 nourishing fluid, and when this has become solidified again to 

 inoculate it in one or two straight lines with matter containing 

 the bacteria to be sown, i. e. to dip a needle pi-eviously heated, 

 or the end of a freshly drawn-out capillary tube into the fluid 

 containing the seeds, and then to draw this needle or the capil- 

 lary tube quickly across the surface of the drop of gelatine 

 nourishing material once or twice; this method, I say, is in- 

 valuable for the study of the gradual changes those bacteria 

 undergo when subjected to incubation, the manner in which 

 they multiply ; further, to ascertain whether the desired or- 

 ganism has been sown, and whether only one kind of organism 

 or several are growing in the nourishing material ; for the 

 glass-cell specimen can be easily examined, even with high 



