Abstract
That newborn infants possess an effective resistance or immunity to certain communicable diseases may be considered a well established fact. This state of resistance endures for variable periods of time but in many instances sooner or later is replaced by susceptibility to the diseases in question, perhaps by an almost universal susceptibility as seems to be the case in measles. The nature of this immunity has been studied by many investigators who have remarked that it may be due to either active or passive immunization during intrauterine life by the passage of antigen or antibody through the placenta, to the transmission of antibodies from mother to child through the medium of colostrum or milk, or to some peculiar insusceptibility of young actively growing tissues to certain types of infection. McKhann and Chu 1 have recently demonstrated considerable concentrations of certain kinds of antibodies in salt solution extracts of human placentas. The subject has not been extensively studied in animals but it is known that antibodies essential to the well-being of the young are transmitted in colostrum as in the protection of newborn calves from colon bacillus infection. Fiadeiro 2 was able to actively immunize newborn pigs by inoculating them with living commercial hog cholera virus within three weeks after birth. No symptoms appeared. In the present study the susceptibility of newborn puppies to experimental infection with the virus of dog-distemper has been investigated.
Six litters of puppies were used in the experimental study. Five of the 6 mothers of these puppies after the birth of the animals were tested for immunity to distemper by an intradermal injection of 10 mg. of dried living distemper virus. All were found to be immune.
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