TEXT-BOOK OF BACTERIOLOGY. 199 



rod-cells. This experiment has since been repeatea times without 

 number, and alwaj^s with the same issue. It may here be men- 

 tioned, too, that Pasteur, after the method of Klebs and Tiegel by 

 filtration, arrived at similar results. 



The great progress which followed in our knowledge of the 

 anthrax poison — that is to say, of the bacillus and its peculiar quali- 

 ties — we owe, in the first place and chiefly, to the investigations of 

 R. Koch, whose brilliant career of general bacteriological research 

 commences here. He saw the development of the cells, the spores 

 in the interior of the cells, and thereby correctly classified anthrax 

 bacilli. What is of still more importance, he succeeded in breeding 

 the rods artificiallj'^ outside the animal organisms, and transmitted 

 them successfully to susceptible animals, thus establishing an ir- 

 refragable proof of their specific importance. 



Since then the study of the anthrax bacillus has not rested for 

 a moment, and has been the means of adding many useful facts 

 to our stock of knowledge. It will therefore be apparent that the 

 anthrax bacillus, the best known of all the bacteria whatever, which 

 indeed serves as a sort of paradigm for all other pathogenic micro- 

 organisms, deserves to be treated very thoroughly and carefully. 



The anthrax bacillus (Bacillus anthracis, the " Bacteridie du 

 charbon " of the French) appears, when taken from a young culture 

 made from the blood of an animal which has perished of anthrax, 

 as a large, evenly-pellucid rod-cell with slightly rounded ends. The 

 separate cells are of various lengths, but are generally somewhat 

 shorter and considerably narrower than a human red blood-cor- 

 puscle. 



The cells are perfectly motionless under all circumstances. The 

 slight trembling and waving of the rods which is sometimes ob- 

 served is always the result of small currents in the surrounding 

 fluid. 



If we place such bacilli in a drop of our ordinary food bouillon 

 and ^inclose the drop in a hollowed slide, we may, under the micro- 

 scope, watch the entire further development of the bacteria step by 

 step. At a somewhat high temperature the rods begin to grow by 

 continuous transverse segmentation and the formation of new cells, 

 and to extend out into the culture medium. After twelve to 

 twenty-four hours the short cells have become long threads, which 

 stretch across the entire field, and only here and there, by a slight 

 constriction or bendmg of the thread, show that they really consist 

 of short pieces joined together. 



The transparent nature of the protoplasm has now disappeared. 

 The cells look clouded and, as it were, granulated. They contain a 



