650 H. M. WOODCOCK. 



sure, by means of good cultures, that all three birds had no 

 trypanosomes in the blood prior to the inoculation, and 

 therefore I considered them to be free from those parasites.' 

 Hence these are in all probability instances of successful 

 inoculation. One case was that of a chaffinch inoculated with 

 the parasites from a redpoll ; another was that of a redpoll 

 inoculated with a culture from a chaffinch. With regard to 

 the third case, that of a chaffinch inoculated with a culture 

 from another chaffinch, I have been very uncertain, owing in 

 part to the difPerent course the infection took, whether the 

 appearance of the trypanosomes in this instance was really 

 due to the inoculation, or was connected with the presence in 

 this bird of Halter idium. I now think this was also a 

 case of successful inoculation, for reasons which are discussed 

 below (see p. 678). 



Attempts to Transmit the Parasites by Mos- 

 quitoes. — It was a great disappointment to me that all my 

 efforts to get mosquitoes infected with the trypanosomes from 

 the birds have been fruitless. Both from Schaudinu's descrip- 

 tion of the infection of Culex with the trypanosomes from 

 the " little owl," as well as on account of the known role 

 of this insect as alternate host of the Proteosoma 

 (Hje mo pro tens) of birds, I thought it most likely that 

 mosquitoes would prove to be the transmissive agents of the 

 parasites — at any rate, the trypanosomes — of the chaffinch 

 and redpoll. 



Unfortunately I was baffled in the very initial stage of all 

 the experiments. I was never able to get the mosquitoes to 

 bite the birds. I have tried at different seasons of the year, 

 late spring, summer, and early autumn, and at periods when 

 the temperature has been quite high for this country. Most 

 of my attempts Avere made with females which were bred out 

 from larvae. None of them, however, showed the slightest 

 inclination to bite. Nor would they feed on a guinea-pig, 

 with which I tried them occasionally. They would only take 



^ I have worked throughout on the assumption that if trypanosomes 

 are present, they will occur, if sparingly, in the general circulation. 



