Disease Transmission and Mans Resistance 327 



future attacks which might be more severe at an older age. The 

 principal source of this protective material is the blood donated by 

 individuals through the Red Cross Blood Donor Programs. 



Gamma globulin is also showing some promise in preventing 

 or attenuating the symptoms of poliomyelitis (infantile paralysis). 

 Such protection is of short duration, since it is an example of 

 passive immunity, but during impending polio epidemics the use 

 of gamma globulin is one of our more encouraging prophylactic 

 measures. In general, one attack of measles or polio confers a life- 

 long immunity to the disease. 



