Leukaemia 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. 



MICEOSCOPICAL 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 4 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. 



Liver. 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 trabeculae, 

 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. Bed 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. 



