IMMUNITY, IMMUNIZATION, AND CURE. ' 57 



^v *';**, ' -^ r ^^. V 



against measles. In the same way it has-been demonstrated, 

 also experimentally, that the immunity established by the 

 various methods of immunization is specifically limited. 

 Preliminary treatment with pneumococcus-cultures protects 

 only against pneumococcus-infection ; inoculation with 

 typhoid-bacilli protects only against infection with these. 

 Also, in the transmission of immunity through blood-serum 

 a specific limitation of the activity of the serum has been 

 demonstrable in all of the cases examined. It is noteworthy 

 that when an animal is protected against several infections 

 through a combination of methods of immunization, its 

 blood-serum likewise is capable of conferring protection 

 against all of these infections. Specificity of immunity and 

 of immunization must be considered the rule, to which, 

 however, there appear to be exceptions. Thus, Roux re- 

 ported at the International Hygienic Congress at Budapest 

 that tetanus-serum is antitoxic not only to tetanus-toxin, 

 but also to snake-venom, while snake-venom-serum in turn 

 proves active against scorpion-poison. 



Heredity of Immunity. Immunity is hereditary : it 

 passes from mother to child that is, it is conveyed with 

 the blood from the mother to the child. In addition, as 

 Ehrlich's experiments have shown, immunity is transmitted 

 through the milk of immune mothers, so that the immunity 

 established by nursing fortifies that which is inherited. The 

 immunizing property of milk corresponds with the immu- 

 nizing power of the egg -yolk of immunized fowl. 



Inherited immunity is naturally only transitory, lasting 

 but a few weeks, and ceasing with the elimination from the 

 organism of the infant of the antitoxins conveyed through 

 the blood during fetal life, and through the milk during the 

 period of lactation (p. 70). The conveyance of antitoxins 

 through the milk during the period of lactation has been 

 demonstrated by Ehrlich for ricin, abrin, and tetanus in the 

 case of mice. Vaillard has been able to confirm the accuracy 

 of these observations. He has, however, shown further 

 that they are by no means universally applicable, and that 

 they are not to be applied without qualification to all 

 species of animals. 



Investigations into the Causes of Immunity. Of the 

 older theories as to the causes of immunity only the reten- 

 tion-theory and the exhaustion-theory need be mentioned. 

 According to the first, there exists a substance that the 



