INFECTION AND IMMUNITY. 475 



in the protective serum nor in the peritoneum of the 

 susceptible animal before receiving the serum, but is 

 generated by the tissues as a result of the specific irri- 

 tation of a something contained in this serum ; in 

 other words, in consequence of a reaction on the part of 

 the peritoneal tissues, or possibly those of the entire 

 animal. 



The experiments of G. and F. Klemperer 1 upon acute 

 fibrinous pneumonia, though too limited in extent to be 

 accepted as conclusive, have, nevertheless, offered a 

 number of most significant suggestions, not only in 

 connection with several obscure features of this disease, 

 but also in relation to the establishment of tissue-resist- 

 ance. 



They found but little difficulty in affording immunity 

 to animals that are otherwise susceptible to the patho- 

 genic action of the organisms concerned in the produc- 

 tion 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 conferred upon the 

 young, during the nursing-period, through the milk 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 



1 G. and F. Klemperer : Berliner klin. Wochenschr., 1891, Nos. 34 and 35. 



2 Animals do not, as a rule, present the pne'umonic 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. 



s Ehrlich : Zeit. fur Hygiene u. Infektionskrankheiten, 1892, Bd. xii. p. 183. 



