Acquired Predisposition and Innnunify. 21 



sliowing a diminished resistive power for a long time {local pre- 

 disposition; locus ininoris resistenticc), as, for example, mucous 

 membranes after catarrhs. 



Predisposition to disease and (a ^natter of extreme impor- 

 tance) immunity against disease may he acquired. It is well 

 known that recovery from certain infectious diseases is accom- 

 panied by an insusceptibility to a repetition of the same affection. 

 This immujiity after previous attacks is at times only temporary, 

 but a few weeks or months in duration, or it may extend over 

 many years or for the entire lifetime. The alteration which has 

 taken place in the condition of the body in such cases is chiefly 

 a chemico-biological one, and although much remains enigmatical 

 concerning it, some insight into the process has been obtained 

 through experimental investigation. Besides the discoveries of 

 Jenner and Pasteur, who gave to mankind facts and methods of 

 the highest importance toward succe^ in combating infections, 

 by which it has become possible by artificial inoculation of an 

 attenuated virus to produce a mild course of the infection and to 

 obtain therefrom immvmity from subsequent attacks of the same 

 disease, there must also be recalled the important discovery that 

 in the blood of man and animals, after attacks of infections, there 

 appear certain substances which are of specific anti-toxic char- 

 acter and are destructive to the virus, and that upon the produc- 

 tion of these substances depend protection and recovery from these 

 diseases. The tissues of the animal body react to irritants which 

 gain access to them. Should a particle of dust or a gnat happen 

 to lodge upon the conjunctiva, such a foreign body acts as a 

 stimulant to the nerves of the mucous membrane, this inducing a 

 free secretion of tears, which usually wash away or dissolve the 

 object. In an analogous manner there is a reaction on the part 

 of the tissues should a toxine or some pathogenic germ (virus, 

 bacterium) come into contact with them, not in this case with a 

 simple secretion to wash away the poison, but nevertheless re- 

 straining the poison and giving origin to substances which are 

 apparently actual antitoxines, or which are able to destroy and 

 thus render harmless the germs of disease. The conditions un- 

 derlying the production of such antagonistic or protective sub- 

 stances, t^eir mode of origin, manner of action and properties, are 

 of extremely complex nature. The numerous experiments of such 

 investigators as Behring, Ehrlich, Brieger, Kitasato, Wassermann, 

 Buchner, Emmerich, Fodor, Nuttall, Nirssen, Bordet, Morgenroth 



