INFECTION AND IMMUNITY. 397 



in the amount of mechanical obstruction offered to 

 the circulation through plugging of the capillaries by 

 masses of bacilli, as detected by microscopic exami- 

 nation of sections of the organs ; indeed, this latter con- 

 dition may often have almost, if not quite, disappeared. 

 We see here an animal dead from the invasion of the 

 same organism that produced death in the first animal, 

 but with little or none of the appearances to which we 

 were inclined to attribute the death of that animal. It 

 is apparent then, that this organism, with which we 

 have been working, can destroy the vitality of an 

 animal in a way other than by mechanically obstruct- 

 ing its bloodvessels ; it possesses some other means of 

 destroying life. Possibly its growth in the tissues is 

 accompanied by the production of soluble poisons, which 

 when present in the blood are not compatible with life. 

 Let us see if the study of another group of infec- 

 tions can shed any light upon the subject. Introduce 

 into the subcutaneous tissues of a guinea-pig a small 

 amount of a pure culture of the bacillus of diphtheria. 

 In three or four days the animal dies. We proceed 

 with our autopsy in exactly the same way that we 

 did with the animals dead of anthrax, and will be 

 astonished to find that the organs, blood, and tissues 

 generally are sterile,' in so far as the presence of the 

 organism with which the animal was inoculated is con- 

 cerned, and by both culture and microscopic methods 

 it is only possible to detect them at the site of inocula- 

 tion, where they were deposited. It is very evident 

 that we have here a condition with which mechanical 

 plugging of the capillaries could have had nothing to 



1 In by far the greater number of cases this is true, but under particular 

 circumstances there are exceptions. 



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