Published online by Cambridge University Press: 15 May 2009
1. Diphtheria toxin-antitoxin mixtures induce a higher immunity in guinea-pigs than sub-lethal doses of toxin; one injection of the mixture being sufficient to produce an immunity lasting in some cases for a period of over two years, as shown by the passive immunity conferred on the offspring.
2. The highest immunity is produced by toxin-antitoxin mixtures containing the most uncombined toxoid.
3. The active immunity of the mother is transferred passively to the offspring.
4. The passive immunity thus transferred usually disappears at the end of two months after birth, and only in rare instances has been recongnised after three months.
5. Immunity is mainly transmitted in utero, and only to a slight extent during lactation.
6. Young bred from does that have been used for a single routine antitoxin test may be able to tolerate 14 times the does of diphtheria toxin fatal for a normal guinea-pig.