THE INFECTIOUS DISEASES. 241 



This bacteriolytic action of specific sera is not peculiar to the so-called anti-cholera 

 serum, but has been observed in other cases for example, in typhoid serum with the 

 typhoid bacillus. Its nature and its bearing on immunity have been considered in an 

 earlier section of this book (see p. 181). 



Other Spirilla Resembling the Cholera Spirillum. 



There are several fairly distinct forms of spirilla, some of which appear to be re- 

 lated to the cholera organism, which have been occasionally found in various situations. 

 One of these is the so-called Vibrio proteus or spirillum of Finkler and Prior. This 

 organism was found by these observers in the dejecta of persons suffering from cholera 

 nostras, shortly after the discovery by Koch of the cholera spirillum, which at first it 

 was thought closely to resemble. The cultural characters, however, abundantly suffice 

 to differentiate the organisms. The Vibrio proteus is slightly pathogenic for certain 

 lower animals, but not for man. 



Several forms of spirilla of somewhat similar general characters have been found in 

 various situations; thus in cheese, by Denecke, 8. tyrogenum ; in a chicken epidemic 

 and in sewage, by Gamaleia and by Pfuhl, Vibrio Metschnikoti ; in the dejecta during 

 a cholera epidemic at Massawah, Vibrio Massawah, etc. Spirillum sputigenum, of fre- 

 quent occurrence about the teeth and in the saliva of healthy persons, is not pathogenic. 



TUBERCULOSIS. 



Tuberculosis is an infectious disease characterized by inflammatory 

 and necrotic processes in the body and incited by the presence and 

 growth of the Bacillus tuberculosis (tubercle bacillus). The most dis- 

 tinctive morphological feature of tuberculosis is the development under 

 the influence of the tubercle bacillus of larger and smaller gray or white 

 or yellow, firm or friable masses of tissue called tubercles. 



The effect on the body cells of the presence and growth of the tubercle 

 bacillus varies considerably, depending upon -the number and virulence 

 of the germs present, the character of the tissue in which they lodge, and 

 the vulnerability of the individual. In general, it may be said that 

 tubercle bacilli may stimulate the connective-tissue cells in their vicinity 

 to proliferation ; or they may excite emigration of leucocytes from blood- 

 vessels and lead to the production of other exudates ; or they may cause 

 death of tissue. Thus the phases of inflammation which are excited by 

 the tubercle bacillus are productive, exudative, and necrotic. The tuber- 

 cle bacillus may incite these changes separately or simultaneously, in 

 the sequence just indicated or in some other; and now one, now another 

 of them may preponderate. 



MORPHOLOGY OF THE LESIONS OF TUBERCULOSIS. 



Tuberculosis manifests itself most often in the form of afu inflamma- 

 tion affecting some one part of the body, as the lungs and bronchial 

 lymph-nodes (the parts most frequently involved in adults), the gastro- 

 intestinal tract or the skin "localized tuberculosis." In a considerable 

 proportion of cases the local lesions induced by the tubercle bacillus 

 are in the form of circumscribed nodules or masses of new-formed cells 

 or tissue which are called tubercles, or if small miliary tubercles. l 



1 The term miliary tubercle, which arose from the coincidence in size between small 

 foci of tuberculous inflammation and some forms of millet seed, is now very liberally 

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