14 Harry C. Schmeisser. 
Lung.—Presents a characteristic structure, entirely different from 
that in the human lung. The tubules mentioned in the macroscopical 
description are seen in cross, oblique, or longitudinal section, forming 
large polyhedral units with wide walls composed of capillaries. The 
intercapillary air spaces communicate with each other and with a large 
central lumen. The latter is lined with a narrow band of smooth 
muscles surmounted by endothelium, frequently cuboidal. The inter- 
tubular fibrous tissue is small in amount, and contains large blood- 
vessels, whose branches extend into the capillary bed. These structures 
are closely packed with red blood cells. Only occasionally does one see a 
lymphocyte. The bronchi resemble those of the human lung. Follicles 
of lymphoid cells are frequently found in the submucosa or outside of 
the bronchi near arteries. 
Bone-marrow.—A low-power picture is very similar to human resting 
marrow, 1. @., one sees a framework of fatty tissue inclosing nests of 
marrow cells. Arteries are filled solely with red blood cells. Venous 
spaces are difficult to determine.. 
Classification of Marrow Cells.—Very thin paraffin sections were 
stained with hematoxylin and eosin and studied under the oil- 
immersion lens. The same cells appear slightly different under these 
conditions than when seen in the Wilson smears of normal and leukemic 
blood. 
Erythrocytes. 
1. Normocyte (a): Elongated, varying in shape, due to pressure. 
Nucleus a solid, black rod or dot (longitudinal or cross section). 
Cytoplasm yellowish-pink and glassy. 
2. Normoblast (6): Round, diameter about width of normocyte. 
Nucleus round, uniformly black. Cytoplasm pink or faintly blue, and 
glassy. Frequently a narrow clear zone is seen about the nucleus. 
3. Megaloblast (b): Same, larger, about length of a normocyte. 
Nucleus slightly picnotic. 
Leucocytes. 
1. Polymorphonuclear myelocyte with eosinophilic rods* (c): 
Round, Nucleus, two or more solid black lobes. Cytoplasm colorless 
with bright red, spindle-shaped rods. 
* These are obviously the polymorphonuclear with eosinophilic rods, the 
polymorphonuclear with eosinophilic granules and the large mononuclear 
cell of the normal blood. 
