30 
Conclusion . — From these experiments it is evident that the tubercle 
bacillus in milk loses its infective properties for guinea pigs when 
heated to 60° C. and maintained at that temperature for twenty 
minutes, or to 65° C. for a much shorter time. 
It should be remembered that the milk in these tests was very 
heavily infected with virulent cultures, indicated by the prompt 
deaths of the control animals. Milk would practically never contain 
such an enormous amount of infection under natural conditions. It 
is justifiable to assume that if 60° C. for twenty minutes is sufficient 
to destroy the infectiveness of such milk when injected into the peri- 
toneal cavity of a guinea pig, any ordinary market milk after such 
treatment would be quite safe for human use by the mouth so far as 
tubercle bacilli are concerned. 
THE EFFECTS OF DEAD TUBERCLE BACILLI. 
In the foregoing work endeavor w^as made to distinguish the 
lesions produced by the dead tubercle bacilli. For comparison 
a number of animals were inoculated with milk containing dead 
tubercle bacilli (killed at 100° C.). The necropsy notes of this 
series, given in Table No. 10, are very mstructive, especially when 
compared with the foregoing work (Tables 1-9). 
Prudden and Hodenphyl ® found ^Mhat tubercle bacilli which have 
been killed by boiling or otherwise, when introduced into the body 
of the rabbit either beneath the skin or into the serous cavities, or 
into the blood vessels and the air spaces of the lungs, are capable, as 
they slowly disintegrate, of stimulating the cells of the tissues where 
they lodge to proliferation, and to the production of new tissue mor- 
phologically similar to tubercle tissue in its various phases. Necrosis 
of the new-formed cells may occur, but this differs in some respects 
from the coagulation necrosis induced under the usual conditions. 
Dead tubercle bacilli are also markedly chemotactic and capable of 
causing local suppuration and abscess.’’^ 
James Miller found that‘s ^‘Dead tubercle bacilli can, then, produce 
changes which in their early stages are the same as those produced 
by the living organism. They differ in acuteness only. When these 
dead bacilli are introduced into the body they attract the leucocytes 
« For further details concerning the effects of dead tubercle bacilli in the body see 
Prudden & Hodenphyl, N. Y. Med. Journ., June 6 and 20, 1891, and Prudden, ibid, 
Dec. 5, 1891. For summary of later work, with bibliography, see Herxheimer, Zieg- 
ler’s Beitr., vol. 33, p. 363; also. Miller, Joiun. Path, and Bact., vol. 10, 1905, p. 351. 
& Delafield, Francis, and Prudden, T. Mitchell: A Text-book of Pathology, 8th ed. 
New York, Wm. Wood & Co., 1907. 1057 p. Ulus. 8°. 
c Miller, James: “The Histogenesis of the Tubercle” Journal of Pathology and 
Bacteriology, 1905, vol. 10, pp. 1-48. 
