koch’s method with tuberculosis 
89 
DISADVANTAGES AND DRAWBACKS. 
“ These are few apart from the certainty that, if largely re¬ 
sorted to, it will be misapplied by many, to other diseases 
than the genuine swine-plague, and will thus fall into disre¬ 
pute. 
“ It can do no good, but only harm to animals that are al¬ 
ready infected, as it can only add to the deleterious products 
with which the germ is charging the system. 
“ Its effect can only be evil if the subjects are allowed to be¬ 
come infected before the chemical products have had time 
to fully affect the system, and to have become eliminated. If 
this is neglected, and early infection is allowed it can only add 
to the mortality. 
“ There is the additional disadvantage that to secure the 
protective products, the production of a virulent germ must 
be kept up either in the bodies of a successive series of 
diseased pigs or in an infusion of pork. The slightest care¬ 
lessness with regard to the seclusion of these fields of poison, 
or as to the disposal of their products, may easily become the 
occasion of a spread of the worst type of the plague among 
unprotected animals.” 
I have quoted thus at length to show that at that date it 
was with me no mere chance suggestion but a settled convic¬ 
tion, based on my own successful experiments and the long 
series of experiments by others, which led up unmistakably to 
this conclusion. And this at a time when Koch, whose ex¬ 
periments on mice had directly indicated the principle 
availed of, had not yet apparently grasped the true signifi¬ 
cance of the ptomaines in conferring immunity, and when 
Toussaint, who was the first to apply the principle, had been 
nonplussed by the unlooked-for results of the Alfort experi¬ 
ment, and led to conclude that his former successes depended 
on a retained vitality in the virus employed. 
In the Department of Agriculture Report for 1882 Dr. 
Salmon again records his lack of success in this method in 
chicken cholera and, while accepting the principle that im¬ 
munity is naturally secured through a power or resistance ac- 
