RELATION OF PATHOGENIC TO SEPTIC BACTERIA. 29 



uniformly turbid, the j^rowth not being limited to the bottom 

 layers ; but soon this changes, and the characteristic nebulous 

 masses are visible at the bottom, while the rest of the fluid 

 is perfectly clear. The first turbidity is due to the uniform 

 distribution in the fluid of the bacilli, isolated and in chains. 



If the vessel in which the cultivation is carried on is kept 

 quiet (I generally keep the test-tubes in a beaker with a layer 

 of cotton wool at its bottom), the peculiar anthrax bacillus 

 growth retains its original naked-eye appearances for a con- 

 siderable time ; shaking the test-tube up after several days' 

 incubation destroys the coherence of the bacillus mass, and 

 this latter breaks up into small flaky particles, which, how- 

 ever, readily sink to the bottom, so that the supernatant fluid 

 again becomes limpid. As long as sufficient nourishing 

 material is present in the fluid the bacillus mass will of course 

 continue to grow in amount, and when this does not any 

 longer take place the fluid is " exhausted." Now, watching 

 the behaviour of the bacillus mass afterwards, i. e. after the 

 mass has ceased increasing, these important facts become 

 obvious : that the bacillus mass becomes gradually smaller ; 

 this diminution is in some instances so rapid and conspicuous 

 that at a first inspection it seems that the cultivation is not 

 the same, but that it might have been changed for another; 

 but there can be no doubt about it if the inspection is made 

 a few days later. This diminution goes on till only a few 

 flaky transparent masses are left in the fluid. Below I shall 

 show what the reason of the diminution is and what the micro- 

 scopical appearances are. During this process of diminution 

 and disappearance of the bacillus mass the fluid remains 

 always perfectly limpid. But I may at once state that this 

 disappearance of the bacillus mass has nothing whatever to do 

 Avith spore formation, as might be at first supposed ; for 

 we know from the researches of Cohn that in a bacillus 

 mass composed of long and convoluted threads, such as the 

 Bacillus anthracis forms in these artificial cultivations, the 

 formation of bright oval spores soon sets in. The newly-formed 

 spores become liberated, the bacillus threads become trans- 



