CHAPTER XXVII. 



Infection and Immunity Mechanism Specific bodies and reactions 

 Doctrines in explanation. 



INFECTION. 



IF we recall the superficial post mortem appearances 

 and the finer details of the pathological lesions caused 

 by the different species of pathogenic bacteria de- 

 scribed in the foregoing pages we might conclude that 

 infection varied with the particular micro-organism 

 causing it. To a certain extent this would be justifiable ; 

 that is to say, the type of lesion characterizing a specific 

 disease is peculiar to that disease and is produced only 

 by the particular micro-organism having the power to 

 excite the disease. But if we take up the various 

 lesions of specific diseases in intimate detail we shall 

 see, as will be shown later, that fundamentally the 

 essential causative feature of infection is of the same 

 nature for all diseases, be the characteristic lesions and 

 clinical manifestations what they may, the apparent 

 differences being referable to dissimilarities of structure 

 and physiological function of the various species of 

 bacteria that excite the several phenomena. Thus, by 

 way of illustration, if we select a group of clinically and 

 pathologically distinct infections, such as anthrax, mili- 

 ary tuberculosis, and diphtheria, and compare the con- 

 ditions recorded at autopsy, little of a macroscopic 

 nature will be discovered to suggest anything that is 

 common to all, and even if the tissues be examined 



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