CHAPTER VIII 1^18] 



SURVEY OF THE FACTS BEARING ON ACQUIRED 

 IMMUNITY AGAINST MICRO-ORGANISMS 



The discovery of attenuated viruses and its application to vaccination against 

 infective diseases. — Vaccination by microbial products. — Vaccination with 

 serums. — The acquired immunity of the frog against pyocyanic disease. — The 

 acquired immunity against vibrios. — Extracellular destruction of the cholera 

 vibrio. — Part played by two substances in PfeiflFer's phenomenon. — Specificity of 

 fixatives. — Phagolysis and its relation to the extracellular destruction of vibrios. — 

 Part played by phagocytosis in the acquired immunity against vibrios. — Fate 

 of the spirilla of recurrent fever in the organism of immunised guinea-pigs. — 

 Acquired immunity against the bacteria of typhoid fever and pyocyanic disease. 

 — Acquired immunity against swine erysipelas and anthrax. — Acquired immunity 

 against the streptococcus. — The acquired immunity of rats against Trypanosoma. 



Certain of the hypotheses on acquired immunity are of as ancient 

 origin as are those on natural immunity. For example, it has for long 

 been known that man is constitutionally refractory to certain diseases 

 which are very fatal to cattle. It has also been recognised that after 

 a first attack of a contagious disease, such as small-pox, measles, 

 scarlatina, typhoid fever, etc., man acquires a lasting immunity ; and 

 that the same rule applies to domestic animals, for example, cattle 

 that have recovered from cattle plague or sheep that have got better 

 from sheep-pox, become refractory against these diseases. 



The discoveries of variolisation and vaccination, as methods of 

 conferring on man a resistance to small-pox, have notably advanced 

 our knowledge upon acquired immunity. The researches on the 

 properties of vaccine had already led to some important results. 

 But it is only since the publication of Pasteur's investigation, carried 

 out with his collaborators Chamberland and Roux, in the first place, 

 and Avith Thuillier later, that we have been able to take up the study 

 of acquired immunity in a really scientific manner. The first in this 



