INFECTION 251 



"hemorrhagic group" we see as a rule typical, fatal septice- 

 mias resulting from the invasion of the body by the organisms 

 causing them; but at times, through influences not fully 

 known, these organisms become modified in their physio- 

 logical functions so that instead of the customary general 

 invasion of the circulating fluids there may be only a very 

 slight invasion and the results of their inoculation are prin- 

 cipally evidenced as local destruction of tissue, sometimes 

 with fatal results. Obviously then these organisms have the 

 power of causing constitutional disturbances, tissue changes 

 and even fatal results without the necessity of their being 

 themselves disseminated throughout the body by way of 

 the circulating fluids. 



As said above the characteristic lesion of tuberculosis is 

 the tubercle, and the peculiarity of the tubercle is necrosis, 

 observable almost from the moment it begins to develop. 

 If tuberculosis be induced through the intravenous injection 

 of rabbits with carefully prepared suspensions of living viru- 

 lent tubercle bacilli the resulting miliary tubercles are always 

 marked by more or less death of tissue at and about their 

 centre, which tissue death progresses as the disease progresses, 

 until it reaches a point easily seen with the naked eye and 

 finally incompatible with life. If on the other hand a similar 

 injection be made with a suspension of tubercle bacilli that 

 have been killed, by heat or otherwise, disseminated nodules, 

 tubercles, will also be found in the internal organs. These 

 may be, histologically, strikingly like those following the use 

 of the living organism ; they are marked by the characteristic 

 tissue death, but it is less in evidence and it is not progres- 

 sive beyond certain limits and the injection does not neces- 

 sarily prove fatal to the animal. As a result of this experi- 

 ment we see that dead bacteria may produce a result differing 



