IMPORTANCE OF BLOOD EXAMINATION.
Whooping-cough is a far more serious disease than is generally supposed, and its diagnosis in the early stage is a matter of great importance, as it is at this time that the infection is most frequently spread. Any measure, therefore, which may help to its early recognition is worthy of careful study and investigation.The examination of the blood in this disease, as in many other infections, has unexpectedly shown a condition which, in a certain number of cases, is abnormal and perhaps of diagnostic value. This condition consists of an increase, both relative and absolute, in the number of the lymphocytes—a lymphocytosis. Several series of cases have been reported showing this increase in these cells, but the number on record is still comparatively small. Therefore I have made some investigations on this subject with the object of determining how frequently this condition is found, how