SOFT CHANCRE. 569 



short duration. The aged, those of low vitality,, 

 and those with pulmonary tuberculosis, have low 

 resistance to infection. 



Although Delius and Kolle were able to produce serum 



. r . Properties. 



a slight increase in the resistance of guinea-pigs 

 by the intraperitoneal injection of cultures, noth- 

 ing like a well-marked immunity was obtained; 

 nor did the serum of immune animals or convales- 

 cent man show increased protective power for 

 other animals. Slatineano, however, obtained 

 serum of some protective value for guinea-pigs, 

 by the immunization of rabbits and guinea-pigs, 

 but it had no curative effect. The results of Can- 

 tani were similar, and both observers noted the de- 

 velopment of bactericidal power, as determined by 

 the Pfeiffer reaction, and of agglutinins. At pres- 

 ent there seems little to hope from vaccination. 



There is said to be some increase in agglutinins 

 in man as a consequence of infection. The agglu- 

 tinating power of the serum of an immunized ani- 

 mal may be as high as 1 to 500 (Cantani). 



VIII. SOFT CHANCRE. 



The independence of soft chancre and syphilis, 

 and the inf ectiousness of the former by inoculation 

 with the purulent secretions of the ulcers, were 

 established long ago. Rollet found that filtered 

 pus lost its infectiousness. 



A large number of observers had found bacteria ^^" us o 

 of one kind or another in the pus and in stained 

 sections of the walls of the ulcers, and probably 

 some of them (e. g., Unna), had seen the bacillus 

 which Ducrey described (1889) and later culti- 

 vated, and which is now proved to be the cause of 

 the disease. The bacillus is very small (0.4x1.5 



