Immunity acquired by natural means 445 



case of diphtheria, and that, consequently, the blood of persons in 

 good health, but containing the diphtheria bacillus in their bodies, 

 may acquire antitoxic power. 



This humoral power, once developed, may even be transmitted 

 from the mother to the foetus and so become hereditary. Abel (l.c.) 

 examined the blood serum of four adult women, taking it from 

 the placenta after parturition. Each time it was found to be dis- 

 tinctly antitoxic against the diphtheria toxin. Later, Fischl and 

 AVunschheim 1 , working in Chiari's laboratory in Prague, studied the 

 blood of new-born children from the same point of view. They 

 showed that in the majority of cases this fluid prevents the produc- 

 tion of a fatal disease in the guinea-pig, in spite of the injection of 

 several lethal doses of very virulent diphtheria cultures. The blood 

 of new-born children is equally capable of neutralising the diphtheria 

 toxin, that is to say, of protecting animals against poisoning by this 

 toxin. The above observers do not doubt that this antitoxic power 

 comes directly from the maternal blood through the placental circula- 

 tion. This fact appears to throw some light on the phenomena of 

 immunity acquired by heredity. 



Until quite recently we have had very vague notions as to the 

 possibility of transmitting to descendants the immunity contracted as 

 the result of recovery from an infective disease or after vaccination. 

 It has long been known that natural immunity may be transmitted 

 hereditarily. Certain families or certain races are characterised by 

 a special insusceptibility to certain infective diseases. It must even [467] 

 be admitted that this innate immunity has been transmitted from 

 generation to generation. It is quite otherwise with acquired immu- 

 nity. We know that as a rule the characters acquired during life 

 are not transmitted to descendants ; it is only in special cases, 

 in the very lowest organisms, such as the bacteria and their allies, 

 that we may observe the conservation of certain acquired characters 

 through an infinity of generations. The attenuation of bacteria or 

 the absence of the formation of spores, once acquired under special 

 conditions, may thus be transmitted to their descendants who develop 

 and live under normal conditions. 



After the discovery of anthrax vaccine by Pasteur, Chamberland 



and Roux, and an attempt had been made to vaccinate large flocks 



of sheep, it was an easy matter to investigate whether immunity 



acquired by the parents was transmissible to their offspring. Several 



1 Prag. med. Wchnschr., 1896. 



