TRYPANOSOMES OF BIRDS 579 



some was also inoculable to other birds (Serinus serinus, S. canarius, 

 Lagonosticta minima, Mariposa phcenicotis, Estrilda cinerea). The infection 

 in canaries was more intense and the mortality higher than in the natural 

 host. These observations serve to indicate the possibility of one species 

 of trypanosome having several hosts (Fig. 235, 12-14). 



Multiplication of T. paddce takes place by longitudinal division in the 

 usual manner, but the dividing forms are only seen in the blood during 

 the early stages of an infection. Later no division forms can be found, 

 and in this respect the trypanosome resembles T. lewisi of the rat. Exami- 

 nation of the spleen and bone marrow did not reveal a greater number of 

 parasites than the blood. In the case of other bird trypanosomes the 

 bone marrow appears to be the site of election, for they can often be found 

 there when the blood-examination has been negative. For instance, 

 Minchin and Woodcock (1911) noted this in the case of T. noctuce of the 

 little owl, and Woodcock (1910) in T. fringillinarum of the chaffinch. 

 These observers pointed out that the trypanosomes were absent from the 

 blood, but were to be found in the bone marrow, especially in winter and 

 spring. 



Thiroux succeeded in cultivating T. paddce in blood-agar media. 



Avian Trypanosomes in General. 



Though a large number of trypanosomes of birds have been given 

 specific names, it is evident that the validity of many of these is very 

 doubtful. Where infections have been studied in any detail, it has been 

 observed that the trypanosomes are very polymorphic. 



Morphology. ^Minchin and Woodcock (1911) noted a great range in 

 size of T. noctuce, the largest forms being found in the winter and spring 

 (Fig. 235, I -10). Thus, there are small forms with a total length of 26-5 

 microns and a breadth of 3-5 microns, intermediate forms measuring 

 44 to 47-5 microns by 5 to 5-5 microns, and large massive forms 54 to 60 

 microns by 5-5 to 6 microns. The small forms gradually grow into the 

 large forms, which are found in winter in the bone marrow. It is supposed 

 that in the summer the small forms are reproduced from the large ones by 

 a process of schizogony, but this hypothetical reproductive process was 

 not observed. The small forms reproduce by longitudinal division, and 

 also give rise to certain stout trypanosomes which, according to the 

 authors, are destined to undergo development in the mosquito. The proof 

 that the mosquito, Culex pipiens, is the transmitting host of T. noctuce, 

 and that the changes undergone by the trypanosome in the stomach of 

 the mosquito, as described by Woodcock, (1914), are true developmental 

 stages, is as yet lacking. It is evident that T. noctuce is markedly poly- 

 morphic in the owl, a feature which, if of general occurrence, renders the 



