738 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
tious diseases by means of dead cultures of their specific bacteria— 
vaccines, so called—must be of the nature of an intensified im- 
munity reaction. What is sought to be accomplished in the latter 
case is the formation in certain uninfected localities—in the subcu- 
taneous tissues, for example—of immunity principles that afterwards 
by escaping into the blood shall assist in the termination of an infec- 
tious process situated elsewhere in the body. Such local foci of im- 
munity as it is designed to create in the subcutaneous tissue are not 
unknown. The pleura can be given a local immunity to the typhoid 
bacilli; the subcutaneous tissue to tetanus toxin, and it is highly 
probable that the normal resistances exhibited by our mucous mem- 
brances to the pathogenic bacteria they harbor are examples of such 
local immunities. 
I fear that I have carried you far afield and into somewhat devious 
paths of immunity to disease. You will, I know, not complain and 
hold it to the detriment of medical science that these paths have not 
been already converted into fine open roads. But you will prefer to 
recall how brief is the time since where the paths now are there were 
only wood and tangle. 
