During the epidemic of smallpox in Southern California in the early part of 1924, the Child Welfare Division of the Los Angeles City Health Department voluntarily vaccinated a large number of infants and children coming to its conferences. This afforded me an opportunity to study the changes in the cellular elements of blood following vaccination. From the very nature of these conferences, it has not been practicable to follow up the blood picture in single cases, as the majority of mothers were of the Mexican race and would not consent to repeated blood examinations. However, examinations were made at certain critical intervals and the results, therefore, are believed to be fairly representative of the general nature of leukocytosis due to vaccination.
REVIEW OF THE LITERATURE
The leukocyte changes following vaccination have been studied but scantily. It has been assumed by many that the blood picture in vaccination stimulates that which