TUBERCULIN 67 



greater resistance. Inasmuch as bacilli with typical avian 

 characteristics have been obtained from human cases, 

 it seems highly probable that avian tuberculosis may be 

 a source of infection. 



Loswenstein found that the ovary was always diseased 

 in affected fowls, and the bacilli were also present in the 

 yolk and in the membranes of the ovum. He found that 

 even boiling eggs to hardness did not destroy the vitality 

 of the bacilli and thought human beings were infected 

 through eating raw or imperfectly cooked eggs. On the 

 other hand, the Commission, comparing the mammalian 

 with the avian viruses, found differences not merely of 

 degree but of kind, though sometimes lesions of a chronic 

 type are produced that are indistinguishable from infec- 

 tions set up by mammalian bacilli. In their final Report 

 they dismissed the infection of man from tuberculosis 

 in birds as a negligible factor. 



Tuberculin. Koch's Old Tuberculin is prepared by 

 growing tubercle bacilli in glycerin veal broth. A copious 

 film formation being needed, flat flasks are used, so that 

 a comparatively large surface is exposed to the air. After 

 six to twelve weeks the culture is evaporated to one-tenth 

 its bulk on a water- bath, and then filtered through a 

 Pasteur filter. 



The injection of 0-002 c.c. into a tuberculous person gives 

 rife to laboured breathing, malaise, and pyrexia, great 

 inflammatory reaction and necrosis occurring round the 

 tubercular focus. If injected into a patient in whom 

 phthisis is dormant, it is very apt to cause the old trouble 

 to break out afresh. 



In the diagnosis of tuberculosis in cattle it is very valu- 

 able, the failures being only about 2 per cent. The injec- 

 tion of 0-1 to 0-2 c.c. causes a rise of temperature of 

 2 to 3 F. above the normal in from eight to twelve hours. 



Koch's New Tuberculin is prepared by drying and 

 pounding young and virulent tubercle bacilli, and ex- 

 tracting with water; the emulsion is then centrifuged. 

 The supernatant fluid (TO) is now discarded. The 

 residue left in the centrifuge is dried, triturated and centri- 

 fuged as before, these processes being repeated until 

 hardly any solid residue is left. The whitish, opalescent 

 liquids resulting from these operations are mixed, and 

 constitute TR. 



