326 BACTERIOLOGY. 



mice, rats, canaries, and dogs are somewhat insusceptible. The pig- 

 eon, sparrow, chicken, and cold blooded animals are immune. Inocu- 

 lation of pure cultures produces tuberculosis in susceptible animals. 

 The bacilli are usually very abundant, but at other times are scarce 

 and difficult to find. Guinea-pig's are extremely susceptible to the in- 

 traperitoneal injection of the tubercle bacillus, whereas rabbits are 

 somewhat less susceptible. There is a marked loss in weight and death 

 may result in 10-14 days. If the dose is small this will not occur for 

 from 4 to 6 weeks, or later. The peritoneum may be studded with fine 

 sand-like tubercles. Larger tubercles are present in the liver, spleen 

 and lungs. Very large tubercles are usually present on the omentum . 

 These have a soft, caseous center and are rich in bacilli. 



The diagnosis of tuberculosis in cattle is effected by 

 the injection of a small dose of tuberculin. A marked rise 

 in the temperature occurs, and may persist for a day or 

 more. 



The staining reaction as given above will usually be 

 sufficient to establish the presence of the tubercle bacillus. 

 In doubtful cases, the animal experiment must be resorted 

 to. It should be borne in mind, however, that a few bac- 

 teria are known which resist decoloration by an acid and 

 hence may be mistaken for the tubercle bacillus. More- 

 over, the mere presence of nodules or tubercles in an animal 

 does not imply the presence of the tubercle bacillus since 

 pseudo-tuberculoses are known which are due to several differ- 

 ent kinds of bacteria. These possible contingencies may 

 be briefly alluded to. 



1. The leprosy bacillus stains like the tubercle bacillus. 

 It can be stained with the ordinary dyes. Moreover, it 

 exists in masses and cannot be transferred to animals, nor 

 can it be grown artificially. The recognition of tubercu- 

 losis in a leper can be effected by means of the animal 

 experiment. Bacilli resisting decoloration with acids have 

 been grown from leprosy material. 



2. The smegma bacillus which may be found in the 

 smegma of the prepuce or of the vulva, stains the 

 same as the tubercle bacillus. While it is resistant to 



