The number of investigations into the state of the blood in pertussis is comparatively small, but there exists a striking uniformity in the results obtained, though accuracy in a review of such investigations is, unfortunately, in some details difficult, because of the varying classifications of the leucocytes which have been adopted.
While the blood changes in pertussis are interesting in themselves, the diagnostic value of the interpretation placed on these changes by the various authors lends additional interest to this study.
With few exceptions, a leucocytosis and lymphocytosis have been noted early in the disease, and diagnostic value has been attributed to their presence. Recently more careful study has well-nigh established a definite series of blood changes in this disease and has demonstrated the value of a blood examination in the early diagnosis of pertussis. The following is merely a brief review, the literature having been quite well covered