﻿124 ASHBURN AND CRAIG. 



demonstrated that it could be seen, though indistinctly, with a power of 2,000 

 diai»«ters, it can hardly be claimed that this organism is ultramicroscopie. In 

 1902, Reed and Carroll (28) filtered the blood of yellow fever patients and 

 proved that the virus passes through a Berkefeld filter by producing the disease 

 by inoculating the filtrate; Rosenau and Francis (29), in 1903, found that the 

 cause of yellow fever passes through a Chamberland B filter. The virus of 

 rabies, according to Remlinger and Riffat Bey (30), passes through the most 

 porous of the Berkefeld filters, but not through other porcelain or diatomaceous 

 filters. In rinderpest, Nicolle and Adil Bey (31) have proven that the cause 

 passes through the Berkefeld and Chamberland F filters; Nocard (32), in 1901, 

 found that the virus of South African horse sickness passed through the Berke- 

 feld filters, and in 1900, McFadyean (33) demonstrated that it also passed 

 through the pores of a Chamberland F and Chamberland B filter. The recent 

 investigations of Dorset, Bolton, and McBryde (34) prove that the organism 

 causing hog cholera is filterable through Berkefeld, Chamberland F and Cham- 

 berland B filters, and as easily through one as the other; they also prove that 

 the organism so long regarded as the cause of the disease — that is, B. cholera 

 suis — is not concerned in the etiology of hog cholera, the disease being produced 

 by the filterable virus. Of the diseases mentioned, the causative organism has 

 been demonstrated, with the highest power of the microscope, in but one — that is, 

 pleuro-pneumonia — and in this instance no morphological details could be distin- 

 guished, the organism appearing simply as a minute motile point. In all the 

 others the parasites are ultramicroscopie. 



In order to determine if dengue belonged to this class of infections, 

 we determined to tr}' the effect of the intravenous inoculation of filtered 

 blood from dengue patients into healthy men. We have experimented 

 in this way upon two men in both of whom we have been successful in 

 producing very typical attacks of dengue accompanied by rather severe 

 symptoms. 



FILTERS USED AND CONTROL METHODS. 



In our filtration experiments we have employed a Lilliput diato- 

 maceous filter, which was tested each time before it was used. Before 

 using, the filter was sterilized and the filtration done under 730 milli- 

 meters pressure. 



After filtering the blood the following control test of the filter was 

 made in each case : A suspension, in nutrient bouillon;, was made of 

 M . melitensis and 8. cholera*, and then filtered through the filter used in 

 filtering the blood; the filtrate was then incubated for two weeks, daily 

 examinations of it being made. The filter in use retained both these 

 organisms, the filtrate remaining sterile for two weeks when it was 

 thrown away. In the control nitrations the same filter was used, after 

 careful sterilization, as was employed for the dengue blood, and the same 

 pressure was maintained during filtration. 



Besides the control test of the filter, we kept in each case a portion 

 of the filtered dengue blood for a period of ten days, making daily 

 examinations, and in one case, several cultures in bouillon. ~No growth 

 was obtained in either the filtered blood or the cultures. 



