II. STUDIES ON THE SERUM OF VACCINATED 

 ANIMALS* 



BY DR. JULES BORDET. 



The subject of immunity has expanded in the last few years. 

 The fundamental problem, to the solution of which a considerable 

 number of researches have been devoted, is to explain how animals, 

 either on account of a natural refractory condition or owing to an 

 artificial immunization, resist the invasion of a given micro-organism 

 and overcome an infection by destroying the bacterium or the 

 poison which it secretes. But there are other facts which also 

 demand explanation. Animals which have been well immunized 

 against a given infection either by repeated injections of bacterial 

 products or of living cultures may be distinguished from normal 

 animals not only by the fact that they henceforth resist this infec- 

 tion, but also, in numerous instances, by the fact that their body 

 fluids, particularly the blood serum, possess properties which are 

 not observed in the non-vaccinated animal. The serum of vacci- 

 nated animals is often preventive and at times bactericidal or 

 antitoxic. It is not sufficient for theories of immunity to explain 

 how an animal that has been vaccinated is fitted to overcome 

 an infection; they must also explain how these new properties, 

 the study of which has so greatly interested bacteriologists, 

 have been formed in the body fluids. The study of the serum of 

 immunized animals forms a new chapter in the history of the 

 struggle between the animal and infective agents, under which head- 

 ing practical results of the highest importance are already inscribed. 

 Any explanation of the phenomena is, however, still far from 

 complete. 



The substances which are present in the serum of vaccinated 

 animals and which endow them with their particular property are 



* Contribution & lY'tude du serum chez les animaux vaccines. Annales de la 

 Societ^ royale des sciences me*dicales et nat. de Bruxelles, IV, 1895. 



8 



