Gr. H. F. Nutt all 
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In this connection I have also a positive experiment to record: 
numerous lice ( H. spinulosus) were removed from infected rats. Great 
care was taken to secure their not being injured. The lice were then 
transferred to clean white rats, being placed close to the skin and 
covered by smoothing back the rats’ hair over them. The lice promptly 
attached themselves to the hairs of the new host. 
Exp. I. 20. iii. 1908. Many lice were removed from a wild rat 
{Mils decumanus ) in whose blood T. lewisi could not be found. The 
lice were transferred to a white rat (A) which had been infected by 
blood inoculation with T. lewisi, and showed trypanosomes in its blood 
on the day before the lice were applied. 
24. iii. 80 lice were removed from rat A and placed on a clean white 
rat ( B). Rat M’s blood showed many trypanosomes at the time when the 
lice were removed. 
26. iii. 30 more lice were removed from rat A and placed on rat B. 
Rat M’s blood contained many trypanosomes. 
3. iv. 1908. T. lewisi found in rat J5’s blood for the first time. 
A second experiment carried out with fewer lice gave a negative 
result. 
Exp. II. 3. iii. 1908. Ten lice were removed from a wild rat (M) 
infected with T. lewisi and placed on a clean white rat B. 
10. iii. Four lice were similarly removed from another infected 
wild rat (M) and placed on white rat B. 
14—24. iii. 1908, and subsequently, rat B’s blood gave negative 
results on examination. 
The first experiment with lice demonstrates that 30—60 lice are 
capable of transmitting T. lewisi from diseased to healthy rats. In the 
second experiment 14 lice failed to transmit the trypanosomes. 
I desire to note that a large number of lice have been examined in 
the course of the last year with a view to studying the development of 
the trypanosome in the louse as described by Prowazek. I have been 
aided in this work by Mr C. Strickland. We have hitherto been quite 
unable to trace any development of T. lewisi in H. spinulosus, and we 
have begun to seriously doubt that such a development actually occurs. 
At present we incline to the opinion that Prowazek was deceived by 
the presence of extraneous flagellates such as are known to exist in 
a number of blood sucking arthropods. Such flagellates have proved 
a fruitful source of error of recent years and in consequence great caution 
is required before reaching any final conclusions regarding what may 
