508 INFECTION AND RESISTANCE 



was the first lesion. The same authors noticed resistance to reinocu- 

 lation in two animals only, and these were young rabbits in the first 

 weeks of life, which, they believed, had been generally syphilized by 

 intracardial injections. Interesting in this connection are claims by 

 Ossola and Truffi who believe that successful skin inoculation in 

 rabbits confers a certain amount of skin resistance and this is in 

 harmony with the belief of Kraus and Yolk, that a specific skin 

 immunity in syphilis is possible. Of great interest to us and of a 

 possible theoretical bearing which we will discuss below, are observa- 

 tions made by the writer with Hopkins and McBurney 146 on 20 

 rabbits which were reinoculated into the testes after apparent healing 

 of lesions in these organs. It appeared that in rabbits the opposite 

 testis can be successfully inoculated before, during, or after, the 

 existence of a testicular lesion on one side, but that reinoculation of 

 the same testis which had apparently returned to normal, at periods 

 ranging from 6 weeks to one year, was not often successful. There 

 is a certain amount of evidence here of a purely local immunity, a 

 matter which we will discuss at greater length presently. Perhaps 

 the difference between rabbits and the higher animals lies chiefly in 

 the fact that syphilis is not generalized in the same sense that it is 

 in man and monkeys, and even though inoculations from the organs 

 of syphilitic rabbits may often result positively, this might signify 

 only that the treponemata have been generally distributed by the 

 blood stream and latently lodged in the organs, without, however, 

 arousing in the tissues any sort of pathological response. This idea 

 would seem to be borne out by the two experiments of Uhlenhuth 

 and Mulzer cited above in very young rabbits since in such animals 

 true generalization seems to be more common. The study of very 

 young rabbits will be continued with this point in view. 



It is apparent from the preceding considerations that resistance 

 to syphilis differs from that acquired in many bacterial infections 

 chiefly in the fact that it does not persist after the disease is over, 

 but probably coexists only with the presence of the living incitants 

 in the body. In this respect it seems to be similar to the conditions 

 prevailing in many protozoan diseases. Thus Schilling 147 cites 

 a case of Trypanosoma Brucei in a steer, experimentally infected 

 by Koch, in which reinoculation was repeatedly negative, this result 

 being at first falsely interpreted as immunity; but six years later 

 Kleine found that the same steer still harbored the trypanosomes 

 in his blood showing that the resistance to reinoculation was not, 

 in this case, an evidence of true immunity, but rather represented a 

 condition of insusceptibility to "superinfection" analogous in every 



146 Zinsser, H., Hopkins, J. G v and McBurney, M. Jour. Exper. Med., 

 1916, xxiii, 329, 341. 



147 Schilling. In Kolle u. Wassermann Handb. d. Path. Mikroorg., xvii, 

 600. 



