﻿ETIOLOGY OF DENGUE FEVER. 107 



2. EXAMINATION OF THE BLOOD. 



In attempting to solve the etiology of dengue and its metliod of 

 transmission, our attention was first directed to the microscopical exam- 

 ination of the blood of patients suffering from the disease. We have 

 already noted the failure of numerous observers to confirm the presence 

 of McLaughlin's or Graham's organisms, and also their negative results 

 as to other blood parasites. Despite these we considered that our work 

 would be incomplete without careful examination of both fresh and 

 stained preparations of the blood, and accordingly we have studied 

 thoroughly, in this respect, a large number of our cases; the blood was 

 examined during every period of the disease, but especially during the 

 first two days and during the terminal rise in the temperature; various 

 staining methods were used, including Wright's, stain and the methods 

 used in demonstrating Treponema pallidum. The latter methods were 

 used very carefully and in numerous cases, as at the time we began 

 our work we were greatly inclined to believe that the organism concerned 

 in the etiology of dengue might belong to the spirochaetse. We have not 

 been able to confirm the results of McLaughlin or Graham, nor have we 

 been able to demonstrate any organism in the blood of dengue patients 

 which we can consider as an etiological factor. 



There is but little in the literature concerning the changes in the 

 blood in this disease, and even Graham's claim that the disease is d\ie 

 to a ha?matozoon which destroys the red corpuscles does not seem to 

 have stimulated research in this direction. We shall, therefore, in this 

 portion of our report, detail the results of our study of the blood which 

 demonstrate that, whatever the cause of dengue may be, it is not an 

 organism that influences to any marked extent the essential characteris- 

 tics of the blood, with the exception of the relative proportions of the 

 various forms of leucocytes. 



(a) Haemoglobin. — In uncomplicated cases the haemoglobin and color 

 index are normal. 



Erythrocytes . — Number : Dengue is not a disease in which anaemia 

 is present. We have made numerous blood counts in severe eases, and 

 have never observed a count lower than 4,500,000 red cells per cubic 

 millimeter, even when the count was made at the termination of the 

 disease. This fact alone appears to us conclusively to disprove the 

 existence of Graham's haamatozoon, which by destroying the red blood 

 corpuscles during its development within them would certainly reduce 

 their number. We have never seen a case of uncomplicated dengue in 

 which the clinical symptoms suggested anaemia. Our observations are 

 borne out by those of Carpenter and Sutton (22), who found that the red 

 blood count in dengue was generally over 5,000,000 per cubic millimeter. 



Morphology : In size the red blood corpuscles are unchanged. Poikilo- 

 cytosis is not commonly observed, but in some eases, during the height 

 of the fever, a moderate degree of poikilocytosis may be present. Crena- 



