Blood Cells From Bone Marrow of the Hatched Chicken
Bone marrow of the adult chicken differs in its general appearance from the bone marrow of the embryo or the recently hatched chick by its abundance of mature erythrocytes. Blast and developmental stages are present but are not so numerous as in the younger ages. These shifts in the incidence of different cell types with age will be described more fully when table 10 is discussed.
Jordan ( 1936 and 1937) has described the bone marrow of several species of birds. In the marrow of all young birds he found lymphoid nodules. These he regarded as centers of hematopoietic activity, especially of erythrocytes. He also observed small vessels plugged with lymphocytes. Jordan and Robeson ( 1942) observed after splenectomy in pigeons that the lymphoid foci and plugged vessels in the bone marrow were increased. Their interpretations need to be reviewed rather critically in the light of observations made since then that lymphoid foci are abnormal in endocrine glands ( Payne and Breneman , 1952), in vessels of nerves and among nerve fibers ( Oakberg, 1950), and in the pancreas ( Lucas, 1949; Lucas and Oakberg, 1950; Lucas, Craig and Oakberg, 1949; Lucas and Breitmayer, 1949; Lucas, 1950 and 1951; Oakberg 1949 and 1951) and in the liver ( Denington and Lucas, 1960; Lucas et al., 1954). The spleen like the bone marrow is a hematopoietic organ, and in addition to the white pulp, contains lymphoid foci. Statistically, these are related to the infection by the agent of avian lymphomatosis ( Lucas et al., 1954). Before similar lymphoid foci and plugged vessels in the bone marrow can be accepted as normal for birds, it should be demonstrated that these are not equivalent to the abnormal lymphoid foci and plugged vessels found in other organs of the body.
A study by Erdmann ( 1917) of chicken bone marrow in tissue culture failed to produce a variety of differentiated cell types from the small lymphocyte. Cultures in a plasma medium showed, first, a degeneration of mature and late polychromatic erythrocytes and some maturation of granulocytes, but this was followed by degeneration. There was no evidence of cell division in myelocytes or in microlymphocytes. Hetherington and Pierce ( 1931) gave a confirmatory observation when they noted that in explants of the buffy coat of chicken blood, all of the lymphocytes degenerated after 48 hours.
Mention has been made of practically all the developmental stages that are to be found in the bone marrow of the hatched chicken but a special effort has been made to bring them all together in a series of drawings under high magnification (figs. 345-399) in order that studies of bone marrow in the chicken can be made as useful for diagnosis and for following the course of diseases as bone marrow studies have been in human medicine.
The erythroblast shown by cell 1 of figure 344 is almost an early polychromatic erythrocyte. Younger blast cells may be seen in figures 345- 347. The last of the three closely duplicates cell 1 of figure 344. Cell 2 is an early polychromatic erythrocyte but shows slightly less condensation of chromatin than either of the cells represented by figures 347 and 348. In the low- power field (fig. 344) there are no good examples of mid-polychromatic erythrocytes, although cell 4 has not passed far beyond this stage. Beside the two cells at 3, there are several additional late polychromatic erythrocytes in the field. Cell 5 is one of these in division, which again demon-