510 INFECTION AND RESISTANCE 



to do this, it will be of advantage to review briefly the attempts at 

 active and passive immunization which have been made in animals 

 and man. 



Metchnikoff and Roux 149 followed their first animal inoculation 

 studies by extensive vaccination experiments. Some of their first 

 work along these lines is perhaps marred to some extent by an in- 

 sufficient recognition of the resistance which depends upon per- 

 sistence of the disease rather than upon true immunity, but a good 

 many of their observations are of fundamental importance. It will 

 be convenient to classify their work and that of others into experi- 

 ments dealing with "active" and those dealing with "passive" im- 

 munization. 



Metchnikoff and Roux first worked with filtered virus and virus 

 killed at 51 C. All their attempts with such material were negative 

 in that the monkeys treated with it could not be regarded in any 

 sense as immunized. In their reports of these experiments they 

 remark that they believed this to be due to an absolute loss of power 

 to incite reaction on the part of the vaccine-material. We emphasize 

 this point here because our own subsequent work inclines us to be- 

 lieve, with them, that the production of a reaction is necessary for 

 the development of any considerable degree of resistance. 



Neisser carried out a large number of attempts at vaccination in 

 which he used extracts of syphilitic primary lesions and of the organs 

 of congenitally syphilitic children, killed by the addition of carbolic 

 acid. Unfortunately he assumed that his extract contained syphilitic 

 antigen because it gave positive reactions by the complement fixation 

 technique of Wassermann, an assumption which we of course know 

 now to be unfounded as far as any relation to the body substance of 

 the treponemata is concerned. This, to our mind, deprives these 

 particular experiments entirely of their negative importance. 



In rabbits a large amount of work has been done by Uhlenhuth 

 and Mulzer. They injected living material from rabbit lesions in- 

 travenously and subcutaneously, without ever observing any evidence 

 of protection against subsequent inoculations. 



Of perhaps the greatest importance in connection with active im- 

 munization are the attempts made upon human beings by different 

 investigators. 



Casagrandi and de Luca 15 tried prophylactic immunization on 

 six human beings by injection of filtrates obtained from primary 

 lesions. Two of these people later contracted syphilis in the ordinary 

 way. 



Possibly the most hopeful results are those obtained by Spitzer ir>1 



149 Metchnikoff and Roux. Ann. de. I'Inst. Pasteur, 1903, xvii, 809; 1904, 

 xviii, 1 and 657; 1905, xix, 673; 1906, xx, 785. 



150 Casagrandi and De Luca. Gior. ital. de mal. ven., 1905. 



151 Spitzer. Wien. klin. Wchnschr., 1905, 45, and 1906, 38. 



