362 MANUAL OF BACTERIOLOGY. 



Weber* obtained a positive reaction in five healthy physi- 

 cians who tried the intraocular injection. The explanation 

 in these cases is to be found in the fact that the men experi- 

 mented upon were in the habit of sitting up reading late by 

 artificial light. 



Immunity from tuberculosis has been attained experimentally to a certain 

 degree. In very old cultures the virulence of tubercle bacilli sometimes becomes 

 greatly diminished. Animals which survive injections of such bacilli may- 

 afterward withstand large doses of virulent bacilli.t 



Friedmannt has succeeded in rendering guinea-pigs and also cattle immune 

 to injection vrith virulent tubercle bacilh by injections of cultures of turtle 

 tubercle bacilli. A single injection of such cultures which are in themselves 

 apparently harmless, confers a high degree of immunity upon cattle. 



Acid-proof bacilli resembling tubercle bacilU have been alluded to a number 

 of times (pages 33, 36, 163, 351). A number of such bacilh have been culti- 

 vated, such as those of butter and grass. Injected into animals they may pro- 

 duce nodules more or less like tubercles. In these nodules they sometimes 

 assume forms resembling the fungus of actinomycosis. The tubercle bacillus ' 

 rarely shows similar forms. All the bacilh of this class, including the tubercle 

 bacillus, sometimes show branching. It is probable that the bacilh of this 

 group are related to the fungus of actinomycosis. § Similar organisms have 

 bfeen found in fishes, in whom they produce nodules resembling tubercles; it 

 is quite possible that the latter organisms are tubercle bacilli, which have been 

 modified by an altered environment. Another acid-proof bacillus has been 

 found which is pathogenic to rats, producing lesions of the skin with nodules; 

 the disease appears in wild rats in certain localities. 



Tuberculosis of Birds. — Fowls, ducks and other birds sometimes suffer 

 from tuberculosis due to a bacillus closely resembhng the tubercle bacillus 

 of mammals. It has similar staining properties. It sometimes grows in long, 

 branching forms. It differs somewhat from the tubercle bacillus of mammals 

 in its cultiiral properties. The Hver is the organ most often affected. Guinea- 

 pigs are much less susceptible to it than to raammahan tuberculosis. Rabbits 

 are somewhat susceptible, though less so than to mammalian tuberculosis. 



Pseudotuberculosis. — Guinea-pigs and other rodents sometimes present 

 lesions macroscopically very similar to those of tuberculosis, in which, however, 

 the tubercle bacilli cannot be found. These affections appear not to be tuber- 

 culosis at aU, and their nature is not well understood. Several organisms 

 have been found in them, all of which are entirely unhke the tubercle bacillus. 



Bacillus Leprae (bacillus of leprosy).— A slim bacillus about 

 4 fi in length. It is probably not motile. It is uncertain 



*British Med. Journ. Feb. 1908. Cited in Journ. Amer. Med. Assn. 

 March i, 1908. 



fTrudeau. New York Medical Journal. July 18, 1903. Salmon. Phila- 

 delphia Medical Journal. June 13, 1903. 



XDeutsche Med. Wochenschr. XXX., No. 46. 1904. 



§Abbott and Gildersleeve. University of Pennsylvania Medical Bulletin 

 June, 1902. Borrel. Bacilles Tuberculeux et ParatubercUleux. BulleHn de 

 I' Institute Pasteur. T. II., p. 409 and p. 505. 



