Leukemia 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 edema. Microscopically, the kidneys 
always show more or less distension of their blood-vessels and inter- 
tubular capillaries with the characteristic leukemic 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 yreatest 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. 
