THE PARASITIC PROTOZOA OF THE RED GROUSE 319 



Personally, I found this parasite in 1909 in three Grouse, all of which were in 

 splendid condition, though in one case the spleen was found to be slightly enlarged. 

 The parasites were in no case numerous, and in one bird only the younger stages 

 of the parasite were seen. However, in the two remaining birds I had the good 

 fortune to find the parasites alive in both peripheral blood and in heart-blood taken 

 from birds freshly killed. Observations were made on the living parasites, both 

 unstained and after colouring them intra vitam with methylene blue (Plate XLVIL, 

 Figs. 17-22). The parasites were also seen while making blood-counts of the 

 avian hosts, when the Leucocytozoon stained intra vitam with the methyl-violet 

 of Toison's fluid. 



The nature of the host-cell is controversial, some authorities considering that it 

 is an erythroblast, others that it is a leucocyte, while the views of some of the 

 observers have changed during the course of their investigations. The 



Relation of 



host-cell clearly does not contain haemoglobin, and no melanin pigment is parasite to 

 excreted by the parasite. The host-cell is at first round or ovoid, con- 

 taining a rather broad and well-marked nucleus, and so the host-cell must be either 

 a mononuclear leucocyte or an erythroblast. Possibly both these types of cells may 

 be infected. The nature of the host-cell is inherently difficult to determine in view 

 of the fact that all the blood-cells of birds are nucleated. Judging by the size of 

 the nucleus of the host-cell (Plate XLVI., Figs. 1-3), I incline to the view that it is 

 a small monouuclear leucocyte or potentially such. Other workers have acknow- 

 ledged the resemblance of the host-cell to a mononuclear leucocyte. However, the 

 matter can only be definitely settled by, researches on the origin and development 

 of the various blood-cells of birds on which our present knowledge is meagre and 

 contradictory running parallel with the researches on infected birds, studying 

 the young stages of the leucocytozoon. 



The host-cell of L. lovati soon becomes drawn out at the ends, that is, the cell 

 becomes spindle-shaped. This is probably due to a deformity of the cell brought 

 about by the movements of the parasite within. Wenyon (1908) considers that 

 some spindle-shaped cells occur normally in the blood of birds and reptiles. I have 

 very rarely seen spindle-shaped cells in the blood of Grouse, though I have found 

 spindle-shaped cells to be more numerous in the blood of fowl-chicks (cf. chapter 

 xiii., Plate XLV., Fig. 18) dying from Coccidiosis. However, I would not suggest, 

 on present evidence, that Coccidiosis is either directly or indirectly responsible 

 for the appearance of spindle-cells in the blood. 



