1908.J BLOOD-PARASITE OP WHITE MICE. 705 



(2) smaller forms, which are cytozoic. At first the latter are free 

 in the plasma, then later, they penetrate usually into mononuclear 

 leucocytes where they feed and grow, finally assuming again 

 the free form, Tery rarely do they occur in polymorphonuclear 

 corpiiscles, but specimens were seen in transitional corpuscles. 



Ko parasites were seen within tissue-cells, whether of liver, 

 heart, spleen, lung, kidney or gut. They seem purely blood 

 parasites, though their presence appears to cause enormous hyper- 

 trophy of cells in their neighbourhood. This was especially well 

 seen in the Kver smears. The parasites were most abundant in 

 these smears and in the portal blood, were fairly numerous in 

 heart and kidney smears, but very few occurred in either lung or 

 spleen preparations, though the latter organ (spleen) was enlarged. 

 Bone-marrow preparations were also made, and schizogony was 

 found to occur therein. 



In the case of the fia-st mouse, extravasation of blood into the 

 gut had occurred and the gut-contents showed free parasites in 

 this blood. Live parasites were studied usually from freshly 

 shed jieripheral blood. 



Examination of the organs of the lice showed vermicule stages 

 of the parasite in the gut and Malpighian tubes. 



The Leucocytozoa were never associated with Trypanosomes in 

 these mice, though such an association has been described for 

 other Leucocytozoa [1] [7]. 



The lice appear to act as mechanical agents in propagating 

 the disease, for lice removed from the third mouse and placed on 

 another resulted in a very slight infection of the hitherto 

 unaflfected one. In the case of L. canis, Gerrard [9] reported 

 that puppies, which were placed together, were cross-infected by 

 the agency of ticks. 



TV. Methods. 

 (a) Fresh material. 



Freshly drawn blood, visually taken from the tip of the tail of 

 the mouse under examination, was mixed with a small quantity 

 of normal saline solution, to which in most cases a little alkaline 

 methylene-blue was added. A drop of the mixture was examined 

 in the well of a micro-slide provided with such a depression, or 

 else on the slide or on the cover-slip, forming a hanging drop in 

 the latter case. The cover-glass was always vaselined round the 

 edges and so air in quantity was excluded from the preparation. 



In this way, living parasites could be observed for several hours. 

 Intra vitam staining with methylene-blue could also be thus 

 -accomplished. Much time was spent in examining the parasites 

 in the fresh state. 



Lice foimd on the third mouse were carefully examined for 

 probable stages in an Invertebrate host. Hemiptera removed 

 :from the mouse were at once dissected in normal saline solution. 

 .Especial attention was paid to the alimentary canal, Malpighian 



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