Circulating Blood of the Hatched Chicken
The "typical" erythrocyte of birds has often been described as an oval cell with an oval nucleus ( Goodall, 1909; Foot, 1913; Magath and Higgins, 1934; and many others). Forkner ( 1929) has described in detail its appearance in vital stained preparations. The nucleus is not quite concentric with the contour of the cell; there is a wider margin at the poles of the cell than at the sides. The cytoplasm takes an orange pink color with Wright's stain and with May- Grünwald Giemsa gives a distinctly more reddish color. The nucleus stains intensely but reveals a pattern of chromatin clumps more or less uniformly distributed. If the nucleus has an oval shape, there are no massive chromatin clumps. If the nucleus is contracted to an elongated rod-shaped structure, dense clumps of chromatin are usually present. A nucleolus is absent.
Low-power views are presented in figures 2 and 3. The slide from which figure 2 was made came from the flock of Single Comb White Leghorn chickens maintained at this Laboratory, and figure 3 was drawn from a set of 25 slides obtained from the same breed at another location, which for convenience has been designated as Laboratory No. 2. Thus, even in these two samples, differences can be observed and probably could be extended if a careful study were made of blood from many sources.
A typical cell is shown in figure 4. It was necessary to do considerable searching to find this "typical"" cell. Examples are shown also in figures 2, 7 and 3, 7. All the other cells deviate from it in shape of nucleus or cytosome or both. The cells may be too round or too elongate or irregular (fig. 3, 5). The nuclei may be too large or too small for the cytosome (figs. 2, 10 and 3, 10); the long axis of the nuclei may not coincide with those of the cells that contain them, or they may be eccentrically placed (figs. 2, 9 and 3, 9) ; the nuclei may not be in the center of the cells and may be blunt at one end and pointed at the other. Most conspicuous of all are the indentations (figs. 2, 11, 12 and 3, 11, 12), constrictions (fig. 2, 13), and protrusions (figs. 2, 14 and 3, 14). Even duplications of the nuclei (figs. 7, 8, and 29) may be found. As far as can be determined, these are all normal cells and in spite of their multiplicity of shape they are all instantly recognizable as mature erythrocytes., because the hemoglobin gives to the cytosome a strong affinity for acid dyes and a nearly homogeneous texture. In some cases a narrow rim of cytosome around the nucleus stains lighter than the more peripheral part, but this is probably an artifact that developed when the cell was flattened in the process of making the smear. This perinuclear space is shown in figure 2 but not in figure 3. The clear space, as suggested, may arise as an artifact but its occurrence in one smear and not in another may be worthy of further study. A perinuclear space appears in all types of blood cells, except the heterophil, when the smear has been fixed in Petrunkevitch No. 2, and stained in May-Grünwald Giemsa (figs. 198-202, 215, and 221). Following this technic the nucleus of the erythrocyte appears to be almost a solid chromatin mass.
Suggestions concerning the origin of multipolar and giant erythrocytes and leukocytes in man have been given by Schwarz ( 1946). He believes these conditions can be traced back to miiltinuclear conditions in the immature stages.
Certain types of variability have significance. Among the 25 blood smears received from Laboratory No. 2 there were several in which the nuclei of the erythrocytes were longer and narrower (figs. 3, 8, and 5) than any found in smears from our flock. Also, the chromatin was more condensed and more heavily stained. The significance is not known but the same type of erythrocyte has been observed in some of the smears