396 BACTERIOLOGY. 



animals known as anthrax represents a type of the 

 condition. If the cadaver of "an animal dead of anthrax 

 be examined by bacteriological methods it will be dis- 

 covered that there is present in all the organs and 

 tissues an organism, a bacillus, of definite form and 

 biological characteristics ; and if the organs and tissues 

 generally be subjected to microscopic examination this 

 same organism will be found always present and always 

 located within the capillaries. At many points it will 

 be seen crowded in the capillaries in such numbers as 

 to almost, if not quite, burst them, and very commonly 

 their lumen for a considerable extent is entirely occluded 

 by the growing bacilli. In such a case as this we might 

 be tempted to conclude that death had resulted from 

 mechanical interference with the capillary circulation. 

 Suppose, however, we subject the cultures obtained 

 from this animal to conditions, either chemical or 

 thermal, that are not particularly favorable to their 

 normal development, and from time to time inoculate 

 susceptible animals with the cultures so treated. The 

 result will be that as we continue to expose our cul- 

 tures to unfavorable surroundings, the period of time 

 that is required for them to cause the death of animals 

 will, in some cases, gradually become extended, until 

 finally death will not ensue at all after inoculation. If, 

 as these animals die, a careful record of the conditions 

 found at autopsy be kept and compared, it will ulti- 

 mately be noticed that the animals that die a longer 

 time after inoculation present conditions more or less 

 at variance with those seen in the original animal. 

 These differences usually consist in a diminution of 

 the number of bacilli that appear upon culture plates 

 from the blood and internal organs, and in a lessening 



