76 BACTERIAL POISONS OF INFECTIOUS DISEASES. 



lesions in the kidney varying from simple degeneration to the more 

 serious condition of acute nephritis. The more severe forms of de- 

 generation were observed in cases which, on account of the intensity 

 of the poison, succumbed shortly after the onset of the disease. The 

 lesions in the human liver differ from those produced experimentally 

 in animals chiefly in the greater frequency of the central situation of 

 the necrosis. The changes in the intestines consist principally of 

 hyperplasia of the lymphoid structures. " The slight extent of the 

 lesions does not indicate the action of toxins absorbed from the ali- 

 mentary canal ; they are probably due to the action of toxins from 

 the blood principally. There is nothing in the character of the le- 

 sions to indicate the elimination of the toxin by the alimentary canal." 

 In the heart fatty degeneration was observed in severe cases of short 

 duration and more extensive degenerations in more prolonged cases. 

 The pathological changes found in the heart are often sufficient to 

 account for the impairment of this organ so greatly feared in this 

 disease. Thrombosis occurs frequently and is due to primary necro- 

 sis of the endocardium. The changes observed in the lungs in man 

 after death from diphtheria are largely due to other microorganisms, 

 among which the pneumococcus is probably the most important. 



Tuberculosis. — In 1865, Villemin demonstrated the infectious 

 character of this disease by inducing it in animals by feeding them 

 upon tuberculous sputum and tissues. In 1868, Chauveau, and, a 

 few years later, Cohnheim experimentally confirmed the discovery of 

 Villemin, which must be regarded as one of the most important con- 

 tributions to medical knowledge made during the nineteenth century. 

 In 1878, Tappeiner showed that tuberculosis might be transmitted 

 by the inhalation of infected dust. However, the nature of the in- 

 fecting agent in" tuberculous tissue remained unknown until 1882, 

 when Koch, after a most exhaustive research covering different mani- 

 festations of tuberculosis in man and some of the lower animals, 

 announced the discovery of the specific bacterium of this disease. 

 This work was so thoroughly done that practically every statement 

 made by Koch in his first report stands to-day unchallenged. The 

 twenty years that have elapsed since that time have each brought its 

 confirmations of the facts then recorded. It is not within the prov- 

 ince of this book to discuss in any detail the bacterium of tubercu- 

 losis, and it must suffice to say that the causal relation of the bacillus 

 tuberculosis to the disease is not now questioned by any competent 

 authority. Every case of tuberculosis is due to infection from a pre- 

 existing case in man or beast. We will concern ourselves wholly 

 with the chemical poisons produced by this bacterium and by virtue 

 of which the symptoms of the disease and death are induced. We 

 may be permitted, however, to call attention to the fact that in its 

 later stages tuberculosis becomes a mixed infection and the chemical 



