948 DISEASES CAUSED BY FILTRABLE VIRUS 



traded a mild form of the disease. A similar observation was made 

 by Kuczynski 37 oil himself. Davies and Weldon 38 in the same year 

 carried out a similar experiment, allowing themselves to be bitten 

 by lice immediately after the lice had fed on trench fever patients. 

 One of them developed trench fever twelve days later. A similar 

 experiment on a volunteer was successfully made by Pappenheimer 

 and Mueller 39 in 1917, but in criticising all these experiments Swift 

 believes that the proof brought was not sufficiently conclusive be- 

 cause of inadequate control. In 1918 two commissions were formed 

 for the purpose of studying the disease. The American commission 

 was aided by a British entomologist, Captain Peacock. The first 

 result of these investigations was that McNee's observation about 

 transmission with whole blood was confirmed, but it was found, 

 in contrast to McNee's results, that the plasma as well as the red 

 blood cells was infectious. It seemed that the blood taken as early 

 as the fourth day of the disease was more infectious than that 

 obtained later. Transmission after filtration through Berkefeld 

 filters did not succeed at first, but Swift records that later, when 

 infectious urine was used, filtration was successful. It was found 

 at this time that, as well as the blood, the urine jf patients is also 

 infectious. 



Careful experiments were made with lice, all of which were 

 reared from eggs and fed on normal subjects, and the non-infectious- 

 ness of these lice was proven by allowing them to feed on eleven 

 different uninfected people. Such lice were allowed to feed several 

 times on trench fever patients and subsequently allowed to feed 

 on twenty-three volunteers, 78 per cent of whom developed trench 

 fever. It did not seem necessary for the lice to be in contact with 

 the skin while feeding, nor was it necessary to produce scarification. 

 In two instances the mere bite of the louse through the meshes 

 of gauze covering the box produced the disease. The incubation 

 time in these louse transmitted cases, varied from fourteen to thirty- 

 eight days, the average being twenty-one. Meanwhile, the British 

 commission found that the excreta of infected lice applied to scari- 

 fied skin could also produce the disease, thus showing that the 



87 KuczynsTci, Eeported from Jungmann, Deut. med. Woeh., 64, 1917, 359. 

 38 Davies and Weldon, Lancet, 1, 1917, 183. 



"Pappenheimer and Mueller, Amer. Red Cross Committee Report, London, 

 1918, Oxford Press. 





