(Jontagious and Epizootic Diseases. 55' 



have been strictly local. Thus a vaccination on the arm 

 protects the whole system against a second occurrence of the 

 disease. A single malignant pustule on the hand fortifies 

 the whole body against anthrax. A swelling no larger 

 than a peach, caiTsed by the insertion of lung-plague virus 

 on the tip of the tail, protects the lungs from attack as if 

 the first manifestation of the disease had been in the lungs 

 tliemselves. This is the more remarkable, that the intro- 

 duction of lung-plague virus into the blood causes no local 

 disease in the lungs nor elsewhere. The germs introduced 

 into the tail caused disease in the tail, but none in the 

 limgs, and as the germs could only reach the lungs by pass- 

 ing through the blood, and as the blood is destructive to 

 these germs, it follows that the germs could never have 

 reached the lungs, and that the vital resistance confei-red 

 upon the lungs by this inoculation in the tail must have 

 been seeui'ed by contact with the chemical products of the 

 growth of the germ, which were thrown into the blood and 

 carried to the lungs and the whole body continuously 

 through the whole progress of the disease. 



Still another fact favors this view. "With some disease- 

 germs (chicken-cholera), dilution of the virus till you can 

 guarantee that no more than one or two germs are intro- 

 duced into the sore by inoculation secures a local and non- 

 fatal in place of a general and lethal disease. The small 

 number of germs introduced have no advantage in jDoint of 

 force over the living nuclei with which they are brought in 

 contact in the tissues, and in the resulting struggle the tissue 

 elements tiiumpli and th6 germs are destroyed. Yet here 

 again the general system is jjrotected against a subsequent 

 attack of the disease, the inoculated germs having diffused 

 enough of their chemical products (ptomaines) through the 

 body to secure this before they died. 



This hypothesis of acquired vital resistance and antago- 

 nism meets the case at every point, and of the four theories 



