U8 SPECIAL BACTERIOLOGY 



out by Behring, is important only from an economic point of view. 

 If of the one hundred animals treated with the serum ninety are cured 

 and ten are killed, the treatment should still be adopted. Experiments 

 to determine the value of this treatment are to be conducted on an 

 extensive scale in the Berlin Veterinary School. 



AVIAN TUBERCULOSIS. 



The bacillus of avian tuberculosis is closely allied to the bacillus 

 of mammalian tuberculosis. 



Microscopical Appearances. It is thinner and more slender than 

 the bacilli found in man and mammals, and club and branched forms 

 are more frequent (see Photomicrograph, Fig. 55). 



Staining Reactions. It is easier stained than the bacilli of man 

 and mammals, but exhibits a similar reaction towards decolorizing 

 agents. 



Biological Characters. It is not so difficult to cultivate as the 

 other forms, growing in ordinary agar and in ordinary bouillon ; but the 

 addition of glycerine to the media assists the growth to a great extent, 

 which, moreover, is much quicker than the growth of the bacillus of 

 mammalian tuberculosis. The cultures are not so dry, but much moister, 

 forming a coherent coating ; and on solid culture media the growth 

 forms a film over the water of condensation. Old cultures exhibit a 

 yellowish colour. 



Differential Characteristics. The bacillus of avian tuberculosis 

 grows just as luxuriantly at 42, 43, 45 C. as at 37 C., a characteristic not 

 exhibited by the bacillus of human tuberculosis, as it ceases to develop 

 at this high temperature. Supposing both forms to be identical species, 

 the effects of the high temperature on the cultures may be due to the 

 avian bacilli having become adapted to a high temperature during their 

 sojourn in the body of the bird, the normal temperature of same being 

 41 to 42 C. The bacilli of avian tuberculosis are more resistant towards 

 heat than the bacilli of human tuberculosis, being first killed by exposure 

 for fifteen minutes at 70 C. 



The bacilli are found in the tuberculous lesions, which are charac- 

 terised by tough masses of nodules, calcareous infiltration often occurring. 

 Giant cells are very scarce. A few cases of avian tuberculosis have been 

 observed in man and mammals. 



Pathogenesis. The most of birds are very susceptible, and can be 

 infected by all the different methods of infection. According to Baum- 

 garten, the spontaneous outbreaks are in most cases congenital. Guinea- 

 pigs and dogs are somewhat refractory, without, however, possessing a 



