596 BACTERIOLOG Y. 



The experiments of G. and F. Klemperer ' upon acute 

 fibrinous pneumonia, though too limited in extent to 

 be accepted as conclusive, presented nevertheless a 

 number of most significant suggestions, not only in 

 connection with several obscure features of this disease, 

 but in their broader bearing upon acquired tissue-resist- 

 ance in general. 



These authors found but little difficulty in conferring 

 immunity upon animals that are otherwise susceptible to 

 the pathogenic action of the organisms concerned in the 

 production of this disease, 2 by the introduction into their 

 tissues of the products of growth of the organisms from 

 which the latter had been separated. The immunity 

 thus produced is seen in some cases to last as long as 

 six months ; again it is seen to disappear suddenly in 

 a way not to be explained. It was seen in one case 

 to be hereditary, probably having been transmitted to 

 the young, during the nursing-period, through the rnilk 

 of the mother, as Ehrlich 3 has shown to occur in 

 animals artificially immunized from abrin, ricin, and 

 robin. 



The energy of the substance that has the power of 

 affording immunity was seen to be very much increased 

 by subjecting it to temperatures somewhat higher than 

 that at which it was produced by the bacteria. The 

 Klemperers found that if this substance was heated to 



1 G. and F. Klemperer : Berliner klin. Wochenschrift, 1891, Nos. 

 34 and 35. 



2 Animals do not, as a rule, present the pneumonic changes seen in 

 human beings. The introduction of micrococcus lanceolatus into their 

 tissues results, in the case of susceptible animals, in the production of 

 septicaemia. 



3 Ehrlich : Zeitschrift fiir Hygiene und Infektionskrankheiten, 1892, 

 Bd. xii. S. 183. 



