226 TUBERCUL OS IS. 



differences, and, reasoning from analogy, we might infer 

 that probably the human subject also would be little 

 susceptible to infection from avian tuberculosis. The 

 question, however, still remains as to whether avian tubercle 

 bacilli can assume the characters and properties of those 

 from mammals, or, in other words, whether they are merely 

 varieties of the same species. Without giving in detail the 

 results of observations on this subject, we may state that 

 there is now sufficient evidence that the one variety can 

 assume the properties of the other. It has been found that 

 occasionally the inoculation of fowls with tubercle bacilli 

 from the human subject produces tuberculosis, and that, when 

 this occurs, the disease can be readily transmitted to other 

 fowls. Also in some cases, inoculation with avian tubercle 

 bacilli produces ordinary tubercle nodules in guinea-pigs 

 and rabbits (Courmont and Dor), and, in other cases, these 

 lesions are found after the bacilli have been passed through 

 the tissues of a number of guinea-pigs. It therefore appears 

 that the bacilli of avian tuberculosis are not a distinct and 

 permanent species, but a variety which has been modified 

 by growth in the tissues of the bird. And probably, to 

 judge from the somewhat conflicting results of experiments, 

 there are degrees of this modification, according to the 

 period of time during which the bacilli have passed from 

 bird to bird. It may also be added that tuberculin pre- 

 pared from avian tubercle bacilli has the same action as 

 the ordinary tuberculin. 



Action of dead Tubercle Bacilli. The remarkable fact 

 has been established by independent investigators that 

 tubercle bacilli in the dead condition, when introduced 

 into the tissues in sufficient numbers, can produce tubercle- 

 like nodules. Prudden and Hodenpyl, by intravenous 

 injection in rabbits of cultures sterilised by heat, produced 

 in the lungs small nodules in which giant cells were occa- 

 sionally present, but no caseation, and which were charac- 

 terised by more growth of fibrous tissue than in ordinary 

 tubercle. The subject has been very fully investigated with 

 confirmatory results by Straus and Gamaleia, who find that, if 



