384 INFECTIVE DISEASES. 



vation inoculated into the subcutaneous tissue, into the peritoneal 

 or pleural cavities, into the anterior chamber of the eye, or directly 

 into the blood stream, produces after three or more weeks artificial 

 tuberculosis in guinea-pigs and rabbits. Dogs and cats can also be 

 infected by experimental inoculation. 



When a trace of tubercular virus is inserted subcutaneously in 

 the thigh of a guinea-pig, in about a week or ten days a chain of 

 enlarged glands will be easily felt in the vicinity of the seat of 

 inoculation. This affords an unfailing test, which can be applied 

 when there is difficulty in ascertaining by the microscope the presence 

 of the bacilli in the material under examination. It also affords a 

 valuable method for testing the effects of antiseptics on tubercular 

 virus. The appearances observed at the autopsy are swollen 

 lymphatic glands, in the neighbourhood of the inoculation, followed 

 by softening and abscess ; enlargement of the spleen and liver, with 

 formation of caseous tubercles ; and tubercular deposits in the lungs, 

 bronchial glands, and peritoneum. 



After inoculation of the eye, grey tubercles appear on the iris, 

 and undergo enlargement and caseation, followed by tuberculosis 

 of the eyeball and organs generally. 



The bacilli appear to be the direct cause of tuberculosis, and 

 the presence of the bacillus in the sputum of patients is a distinctive 

 sign of the existence of this disease. The detection of the bacillus 

 has, consequently, become a test which is constantly applied. 



The bacilli are found in all tubercular growths of man, monkeys, 

 cattle (Perlsuckt), birds, and many other animals, and in cases of 

 artificial tuberculosis, in rabbits, guinea-pigs, cats, etc. In man the 

 bacillus can be detected in the tissues, in the sputum, in the blood, 

 and in the urine. 



Tuberculosis may also be produced by inhalation and feeding 

 experiments. The channels of infection in man are also most 

 probably the pulmonary and intestinal mucous membranes. The 

 possibility of inoculation of skin wounds is open to doubt. The 

 bacilli or their spores are inhaled from the air, or taken in with 

 food. Morphologically identical bacilli have also been observed, but 

 very sparsely, in sections of lupus. 



METHODS OF EXAMINING THE TUBERCLE BACILLUS. 



Numerous methods have been recommended for examining the 

 tubercle bacillus. A few of these will be described, as many are 

 only of historical interest. 



