RESISTANCE OF TUBERCLE BACILLUS 249 



Woodhead^ fed six guinea-pigs with milk from a tuberculous 

 udder, which had been exposed for fifteen minutes to 60" C, with- 

 out effect Similarly, milk heated for thirty minutes at 60" C. had 

 no effect on guinea-pigs fed with it. On the other hand, milk 

 heated fifteen minutes at 60^ C, and injected into the peritoneal 

 cavity produced tuberculosis in two of three guinea-pigs. Of 

 three guinea-pigs inoculated in the same way with milk heated at 

 60 C. thirty minutes one became tuberculous. In another series 

 of experiments with milk from a tuberculous udder no disease 

 resulted from milk heated twenty-five or more minutes. Milk 

 heated for shorter periods was not injected. Experiments were 

 also made with milk to which ground and minced tuberculous 

 tissue had been added. In such milk, artificially infected, the 

 tubercle bacillus was in some instances still alive after two hours 

 exposure to 60° C- 



The next series of experiments to which reference must be 

 made were those by Theobald Smith in 1897,^ The basis of his 

 experiments was artificial cultures and caseous material from 

 tuberculous cattle. Milk was at first used exclusively as the 

 suspending fluid, but at a later stage it became necessary to use 

 simpler fluids, such as bouillon, distilled water, and physiological 

 salt solution to clear up the discordant results obtained with milk. 

 The manipulations were modified from one test to another, either 

 to remove some supposed defect of former methods, or to answer 

 certain new questions which former tests had raised. Blood serum 

 from the dog set at 75° to 76' C. was used exclusively as the 

 culture medium. The suspensions were made by rubbing masses 

 of bacilli against the inner surface of sterile test-tubes near the 

 bottom until a fairly homogeneous coating had been formed. The 

 rubbing was done with a heavy platinum wire beaten into the 

 form of a slender spatula. The suspending fluid was then poured 

 into the tube and thoroughly stirred. The resulting suspension 

 contained many clumps of bacilli made up of a few to thirty or 

 more rods. The tubes thus prepared were exposed in a water- 

 bath, or else other tubes were used to which definite quantities 



' Report of the Royal Commission on Tuberculosis, 1895, P- I45- ^^^ whole 

 of the Inquiry iii. is full of instruction respecting this matter, especially pars. 

 103 et seq. 



- See also Galtier's experiments, Com/>. Rend, de la Soc. de Biolo^e, 1900. 

 Bang, Brit. Congr. on Tuberculosis, 1901, vol. iii., p. 592. Also Delepine, Ibid., 

 vol. iii., p. 602. 



^ Journal of Experitnenial Medicine, 1899, vol. iv., p. 217 et seq. See alsb 

 vol. iii., 1898, p. 451. 



