135 
THE EXPERIMENTAL TRANSMISSION OF THE SPIRO- 
CHAETE OF EUROPEAN RELAPSING FEVER TO RATS 
AND MICE. 
By H. BA von, 
Beit Memorial Research Fellow. 
(With 3 Text-figures.) 
On clinical grounds alone sufficient evidence is available to 
postulate that European relapsing fever and Central African tick-fever 
are caused by different, though closely allied, organisms. However, 
as the spirochaetes of both diseases are morphologically identical 
(Schellack, 1908; Darling, 1909), I should like to record some ex¬ 
periments and observations I made during the winter of 1910-11 in 
Moscow, so as to give an exact impression of the difficulty or ease with 
which Spirochaeta recurrentis can be transmitted to mice when com¬ 
pared with S. duttoni under the same conditions. Moreover, I wish to 
describe some appearances in S. recurrentis, the exact counterpart 
of which have not so far been published in the case of any blood 
spirochaete. 
For comparative purposes I also studied the behaviour in mice of 
strains of 8. duttoni and S. novyi which were kindly given me by 
Prof. Martin Meyer, of Hamburg. 
Previous researches on the direct transmission of 8. recurrentis from 
the human being to the mouse and rat were carried out by 
Gabritschewsky in 1906. On this occasion he reported having 
transmitted the infection by passage through three animals, but no 
further. Mice which had withstood one infection could not be re¬ 
infected. 
Following Gabritschewsky, Uhlenhuth and Haendel (1907) got 8. 
recurrentis to thrive in mice and rats, after passage through a monkey. 
It is interesting to note that they procured the blood from Moscow, 
in a leech. Shortly after Uhlenhuth and Haendel’s results were 
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