Leukemia of the Fowl. 13 
rich in red blood cells and fat. Lower part of middle third frequently 
consists of a solid, yellow column of fat. The marrow cavity may be 
almost occluded by bony septa. 
MICROSCOPICAL EXAMINATION. 
Cervical Lymph-gland.—Section shows lobules of parenchyma, 
‘separated by fatty tissue. Each lobule is surrounded by a delicate 
fibrous capsule and contains a very fine reticulum, in which the 
lymphocyte is diffusely scattered. This is a small, round cell with a 
round, deeply staining, picnotic nucleus, usually incompletely sur- 
rounded by a narrow rim of pink cytoplasm. Sometimes red blood 
cells are associated with the lymphocyte, but mostly they are confined 
to and form the sole occupants of the numerous capillaries. They 
appear as elongated, yellowish-pink cells, with a solid black rod or dot 
for nucleus, according to whether this is seen in longitudinal or cross 
section. Scattered through the lobule are small, sharply outlined, 
hyaline structures, which Kon * considered as corresponding to Hassall’s 
corpuscles of the thymus. 
Thyroid.—Consists of polyhedral acini, which vary in size, are lined 
with cubical epithelium and filled with granular colloid. They are 
separated from each other by a small amount of fibrous tissue, rich 
in blood capillaries. Sometimes accumulations of lymphocytes may be 
seen near the larger vessels. 
Parathyroid.—Within its capsule is seen a prominent reticulum filled 
with closely packed cells, whose nucleus is round or oval, semivascular 
and larger than that of the lymphocyte. 
Liwer—The lobule is difficult to limit. Periportal spaces are not 
easy to find. They consist of one or several arteries, a vein, one or 
several gall-ducts, and very little or practically no fibrous tissue, usually 
free from infiltrated cells, although lymphocytes may be present dif- 
fusely or in small follicles. The liver cells are arranged in trabecul, 
separated by capillaries. All blood-vessels and capillaries are filled 
exclusively with red blood cells. 
Spleen.—The Malpighian bodies are indistinct, numerous, closely 
packed, composed of masses of lymphocytes surrounding very small 
arteries. Red blood cells are limited to the pulp, where they occur 
more or less in clusters, although one is unable to demonstrate sinuses 
or inclosures of any kind. The lymphocytes are also diffusely scattered 
throughout the pulp. Veins tend to be rich in lymphocytes and 
poor in red blood cells ; the artery shows the opposite picture. 
