ANTI-PLAGUE SERUM. 323 



ties as well, providing it be employed at an early stage 

 of the disease. In 1896 Yersin l used the serum of arti- 

 ficially immunized horses in the treatment of plague 

 in human beings. Of 26 persons (3 in Canton and 23 

 in Amoy, China) who received injections of the serum 

 during the early stages of the disease, in no case later 

 than the fifth day, only 2 died. Comparing this mor- 

 tality of 7.6 per cent, with the mortality of 80 per cent, 

 among persons in this epidemic who were treated in 

 other ways, he feels justified in regarding the method as 

 worthy of consideration. 



ANTI-PLAGUE SERUM. During recent years a great 

 deal of further investigation has been made in order to 

 ascertain the pathogenic properties of bacillus pestis, 

 and to obtain a more detailed knowledge of immunity 

 against infection by this organism. The studies of the 

 latter class include the estimation of the quantitative 

 value of the pest-serum when tested on different species 

 of animals, its protective and curative properties when 

 employed on such animals, especially its protective 

 properties against experimental inhalation pneumonia 

 and infection by feeding pi ague- infected materials. 

 These observations have been carried out by several 

 pest commissions namely, those of Germany, Austria, 

 and Egypt as well as- the detailed investigations of the 

 Institutes for Infectious Diseases at Berlin, at Berne, 

 and the Pasteur Institute at Paris. 2 The preparation 

 of the pest-serum is conducted as follows : Horses are 

 injected at first with dead cultures of bacillus pestis, 

 then with increasing doses of living agar cultures of the 



1 Annales de 1'Institut Pasteur, 1897, p. 81. 



2 The important literature bearing on this subject is appended to 

 the report of Kolle, Hetsch, and Otto (Zeitschr. f. Hygiene, Bd. 38, 

 p. 368). 



