﻿ETIOLOGY OF DENGUE FEVER. 109 



that the leueopenia is progressive, being most marked upon the fifth or 

 sixth day of the disease. 



Morphology : We have observed no morphological changes in the leu- 

 cocytes, nor any evidence of the presence of a leucocytozoon. 



Differential blood count: From the studies of Carpenter and Sutton, 

 and later of Stitt, the differential leucocyte count in dengue bas assumed 

 considerable diagnostic importance, and taken together with the leu- 

 eopenia appears to us to be entitled to very careful consideration in the 

 differential diagnosis of dengue, yelloAV fever, malaria, and the eruptive 

 fevers. 



Carpenter and Sutton (22), from their examinations, conclude that in dengue 

 there is always a leueopenia, and generally an increase in the small lymphocytes 

 and in the eosinophiles, the latter occurring late in the disease. 



Stitt (20) made differential leucocyte counts at varying periods of the disease. 

 He found that a marked variation occurred in the different forms of the leucocytes 

 at different periods, there being at first a large increase in the small lymphocytes, 

 succeeded by a greater increase in the large lymphocytes, and finally, during the 

 terminal eruption, a most marked increase in the large mononuclears. 



Because of lack of time we have made comparatively few differential 

 leucocyte counts, but our results have been supplemented by those of 

 Lieutenant Vedder, Medical Department, United States Army, stationed 

 at Fort William McKinley, who kindly volunteered to assist us in this 

 direction, and whose tables and remarks are given below. From our 

 own observations we are loath to lay much stress upon the variation in 

 the relative proportion of the large and small lymphocytes, as does Stitt, 

 for in many instances we have not found a constant relationship between 

 the variety of lymphocyte which is increased and the period of the disease, 

 but we have found a constant leueopenia, a decrease in the polymorphonu- 

 clears and an increase in small lymphocytes. In one of our experimental 

 cases (Case 9) in whom we produced a severe attack of dengue by the 

 intravenous inoculation of the filtered blood from another experimental 

 case, the leucocyte counts made upon the first, third and sixth days of 

 the disease, well illustrate the changes described b} r Stitt, as will be seen 

 by the following record : 



First day of disease: 



Polymorphonuclears 50 



Small lymphocytes 41 



Large lymphocytes 7.5 



Eosinophiles - 1-5 



Third day of disease : 



Polymorphonuclears 52 



Small lymphocytes - 30 



Large lymphocytes 8 



Eosinophiles - 4 



Sixth day of disease: 



Polymorphonuclears 48 



Small lymphocytes 14 



Large lymphocytes 32 



Eosinophiles 



