182 MICRO-ORGANISMS AND DISEASE. [CHAP. 



that is to say, that it is neither owing to their appropriating 

 from the blood-corpuscles the available oxygen necessary for 

 their multiplication (Bellinger) and thus producing death by 

 asphyxia, nor to their mechanical effect in plugging up the 

 capillaries of vital organs, a theory upheld by some observers 

 from the fact that in most cases the capillaries appear filled with 

 the bacilli, and in some cases in extensive regions, lung, kidney, 

 and spleen, the capillaries are almost occluded by the bacilli. 

 We must assume, then, that although as a rule immediately 

 before death all the conditions are present to enable the bacilli 

 to multiply readily and to produce a large crop, this is not 

 necessarily connected with the cause of death, being in fact in 

 consequence of the animal being in articulo mortis ; but that 

 the immediate cause of .death is the chemical alteration 

 produced by the bacilli in the blood and tissues. For pro- 

 ducing this effect it is not necessary to have more than a certain 

 number of the bacilli. As soon as this number is reached 

 death follows. The same may be said of other pathogenic 

 organisms. Thus for instance in the case of tubercle-bacilli, 

 after the introduction of these into the subcutaneous tissue of 

 a guinea-pig, multiplication takes place, and after they reach a 

 certain number, the nearest lymph-glands become swollen and 

 inflamed and then caseous ; but this stands in no relation to 

 the number of the bacilli, for in some instances the microscopic 

 examination reveals only very few bacilli, they are scattered in 

 very small numbers over very wide areas. And the same is 

 observed in the tuberculous deposits of the internal organs. 

 In some of them the bacilli are exceedingly scarce, while in 

 others neither more nor less advanced they are numerous. 

 Here also we must assume that as soon as a certain, perhaps 

 even small, number of the bacilli has been produced the 

 chemical effect produced is sufficient to be the cause of a 

 certain pathological change. In glanders, the nodules in the 

 skin and lung reveal sometimes, even under the most careful 

 examination after approved methods, the presence of but very 

 few bacilli. In swine-plague, in the lungs, which in severe 

 cases are enormously affected, sometimes only very few of the 

 pathogenic organisms can be discovered. It follows then that 

 the pathological condition brought about by the organisms is 

 not due to the direct action of their numbers ; but is an indirect 

 sequence, brought about by definite chemical alterations in the 

 blood or tissues as the case may be. 



In this we may assume two theories as possible : () It is 

 possible that these chemical effects are produced by the 

 presence and growth of the organisms, as truly as in the 



