502 INFECTION AND RESISTANCE 



tions of the disease. The autoinoculation experiments of Ehr- 

 mann 131 also would tend to show that the resistance of the luetic 

 subject is a relative one only. Ehrmann succeeded in producing 

 positive autoinoculation-products in 45 syphilitics with papular erup- 

 tions. Control inoculations with sterile water were negative. Al- 

 though his observations and those of Finger and Landsteiner, with 

 other similar ones, teach us that superinfection during the disease 

 is possible the nature of the lesions, their short incubation time, and 

 their exceptional character when averaged with the total of such at- 

 tempts, prevent them from invalidating the conclusion that there is 

 a resistance at this stage higher than that of the normal subject. 



We may conclude, therefore, concerning the secondary period of 

 the disease, that the luetic individual has acquired a resistance which 

 while not absolute is at least very high, and protects him from fresh 

 external inoculation, although at the time his disease may still be 

 progressing and in no sense overcome. 



3. During the late stage of syphilis, the stage at which, according 

 to the more or less arbitrary divisions of Ricord, we are accustomed 

 to speak of it as "tertiary," the resistance is still manifest, though 

 apparently not so regularly potent as during the preceding "secon- 

 dary" period. JSTeisser expresses himself with great caution and 

 accepts few, if any, of the observed reinoculations of tertiary cases 

 as surely representing unquestionable freshly acquired infections. 

 Nevertheless, taking into consideration a detailed study of individual 

 reports, he concludes that resistance during the late stages is pro- 

 nounced but already beginning to wane. He himself in the Fest- 

 schrift to F. Joseph Pick in 1898 cites a case of the development of 

 a chancre in a tertiary case which, however, was not followed by 

 constitutional symptoms. 



r- 4. In the preceding paragraphs we have concerned ourselves 

 entirely with questions of "superinfection," that is, the implantation 

 of the syphilitic virus into subjects still suffering from manifesta- 

 tions of the disease. A problem of equal theoretical, and of much 

 greater practical importance, is that dealing with true "reinfection." 

 .By "immunity" in the ordinary sense, we mean an increased resist- 

 ance to specific infection which persists for a more or less prolonged 

 period after the active disease has been overcome and the causative 

 agents removed from the body. It is not easy to draw conclusions 

 -concerning this point from observations on human beings, since it 

 is most difficult to decide, even with the aid of serological methods, 

 whether or not a given case is cured in the bacteriological sense; 

 for syphilis is preeminently the disease in which there occur fre- 

 quent and prolonged latent periods terminated, often after lapses of 

 years, by the reappearance of foci of a grave nature. 



Moreover, our own experiments both with syphilis in rabbits and 



131 Ehrmann. Cited from Neisser, loc. cit. 



