BACILLUS ANTHRACIS. 301 



early part of the present century much attention was paid to it, and, with a 

 view to finding out its nature and means of spread, various conditions attach- 

 ing to its occurrence, such as tliose of soil and weather, were exhaustively 

 studied. PoUender in 1849 pointed out that the blood of anthrax animals 

 contained numerous rod-shaped bodies which he conjectured had some causal 

 connection with the disease. In 1863 Davaine announced that they were 

 bacteria, and originated the name bacillus anthracis. He stated that unless 

 blood used in inoculation experiments on animals contained them, death did 

 not ensue. Though this conclusion was disputed, still by the work of Davaine 

 and others the causal relationship of the bacilli to the disease had been nearly 

 established when the work of Koch appeared in 1876. This constituted that 

 observer's first contribution to bacteriology, and did much to clear up the 

 whole subject. Koch confirmed Davaine's view that the bodies were bacteria. 

 He observed in the blood of anthrax animals the appearance of division, and 

 from this deduced that multiplication took place in the tissues. He observed 

 them under the microscope dividing outside the body, and noticed spore 

 formation taking place. He also isolated the bacilli in pure culture outside 

 the body, and by inoculating animals with Jhem, produced the disease 

 artificially. In his earlier experiments he failed to produce death by feeding 

 susceptible animals both with bacilli and spores, and as the intestinal tract 

 was, in his view, the natural path of infection, he considered as incomplete 

 the proof of this method of the spontaneous occurrence of anthrax in herds 

 of animals. Koch's observations were, shortly afterwards, confirmed in the 

 main by Pasteur, though controversy arose between them on certain minor 

 points. Moreover, fiirther research showed that the disease could be pro- 

 duced in animals by feeding thera with spores, and thus the way in which the 

 disease might spread naturally was explained. 



The Bacillus Anthracis. — Anthrax as a disease in man is of 

 comparative rarity. Not only, however, is the bacillus anthracis 

 easy of growth and recognition, but in its growth it illustrates 

 many of the general morphological characters of the whole group 

 of bacilli, and is therefore of the greatest use to the student. 

 Further, its behaviour when inoculated in animals illustrates 

 many of the points raised in connection with such difficult 

 questions as the general pathogenic effects of bacteria, immunity, 

 etc. Hence an enormous amount of work has been done in 

 investigating it in all its aspects. 



If a drop of blood is taken immediately after death from an 

 auricular vein of a cow, for example, which has died from 

 anthrax, and examined microscopically, it will be found to 

 contain a great number of large non-motile bacilli. On making 

 a cover-glass preparation from the same source, and staining with 

 watery methylene-blue, the characters of the bacilli can be better 

 made out. They are about 1.2 /i thick or a little thicker, and 



