Leukaemia of the Fowl. 29 



delicate lines, or even one or two nodules, the largest 0.5 cm. in diameter. 

 Again, they may appear diffusely gray. In the one case, they were large, 

 succulent and translucent, due to oedema. Microscopically, the kidneys 

 always show more or less distension of their blood-vessels and inter- 

 tubular capillaries with the characteristic leukaemic blood, in which 

 white blood cells, at times, seem even to exceed the normocytes, and in 

 which the large mononuclear predominates. When capillary distension 

 is moderate, the tubules appear normal ; but at times they are so enor- 

 mously over-filled as to cause extreme atrophy and degeneration of the 

 tubular epithelium, resulting frequently in circumscribed areas devoid 

 of any parenchyma. These areas tend to form a kind of zone about the 

 larger blood-vessels. The glomeruli are surprisingly free. The walls 

 and perivascular tissue of some of the vessels are infiltrated with 

 actively generating myeloid cells, especially the large mononuclear. 



Bone-marrow. This is always involved, usually more or less char- 

 acteristically, being increased in amount, moderately soft and red, mot- 

 tled with countless gray dots to slightly larger areas, or it may be dif- 

 fusely gray. In either case the fat is absent entirely and red blood 

 cells are very scarce. The marrow may be involved as a whole or only 

 in part. Now and again it has been converted into a uniformly gray, 

 dry and slightly firm column, which bulges from the marrow cavity. 

 In such cases it is obviously very rich in white cells, poor in red cells and 

 fat. Microscopically, the normal structure of the marrow is greatly 

 changed. The fatty tissue has completely disappeared and the marrow 

 cells are closely packed in a solid mass, in which the normocyte is 

 rather inconspicuous. The arteries in the center of the marrow are 

 poor in blood. One or two contain a few normocytes and large mononu- 

 clears. The description of the red and white cells, which are present 

 agrees with that given under normal marrow. Possibly the large 

 mononuclear is more commonly polygonal, due to pressure. Mitoses of 

 both the large mononuclear and the erythrocytes are common especially 

 the first. The order of predominance has changed from the normal. 

 The large mononuclear myelocyte is present by far in greatest numbers ; 

 the normoblast, megaloblast and mononuclear myelocyte with eosino- 

 philic granules follow in about equal numbers; the normocyte comes 

 last. Both types of polymorphonuclear cells, as well as the lymphocyte, 

 mast cells and platelets were not seen at all. Mitoses of the mononu- 

 clear myelocyte with eosinophilic granules were not demonstrated. 



