94 ESSENTIALS OF BACTERIOLOGY. 



water fuchsin can be used, but the sections must remain in the 

 stain over night. 



The resisting action of the bacillus to acids is supposed to 

 be due to a peculiar arrangement of the albumen and cellulose 

 of the cell rather than to any particular capsule around it. 



Patliogenesis. When a guinea-pig has injected into its peri- 

 toneal cavity some of the diluted sputum containing tubercle 

 bacilli it perishes in about three weeks, and the following 

 picture presents itself at the autopsy : at the point of inoculation 

 a local tuberculosis shmcs itself, little tubercular nodules contain- 

 ing the characteristic bacilli. In the lungs and the lymphatics, 

 similar tubercles are found, a general tuberculosis. 



If the animal lingers a few weeks longer, the tubercles become 

 necrosed in the centre and degeneration occurs, the periphery 

 still containing active bacilli, cavities having formed in the 

 centre. 



Since the bacilli die in course of time, killed by their own pro- 

 ducts, their number forms no correct guide of the damage present. 



Even their absence in the sputum does not preclude ihe ab- 

 sence of a tubercular process. It is their presence only that 

 warrants a positive declaration. 



They are found in the blood only when a vessel has come in 

 direct contact with a tubercular process through rupture or 

 otherwise. They have been found in other secretions, milk, 

 urine, etc. 



Mn is infected as follows : 



Throutjh wounds. Local tuberculosis. 



Throwjk nutrition. Milk of tuberculosis cows. 



Phthisical patients swallowing their own sputum and causing 

 an intestinal tuberculosis. 



Inhalation. This is the most usual way, probably constitu- 

 ting the cause in , 9 (t of the cases. 



The sputum of phthisical patients expectorated on the floors 

 of dwelling-houses in handkerchiefs, etc., dries, and the bacilli 

 set free are placed in motion by the wind or rising with the dust 

 are thus inhaled by those present. When the sputum is kept 

 from drying by expectoration in vessels containing water, this 

 great clanger can be avoided. 



