448 H. E. JORDAN 
generally of the smaller lymphocyte type with granular vesicular, 
nucleus; this may grow into the larger type. Extravascularly, 
the original hemoblast is more generally of the large lymphocyte 
type (figs. 34 and 35); this may divide mitotically to form small 
lymphocytes. These marrow types correspond with the large 
and small lymphocytes of the blood smears, except that in the 
latter the originally basophilic homogeneous cytoplasm of the 
marrow cells becomes granular‘and may in addition elaborate 
metachromatic granules. Similarly, the small lymphocytes form 
metachromatic granules in becoming thrombocytes within the 
blood spaces of the red marrow. 
3. The development of the eosinophilic leucocytes. ‘The eosino- 
philic myelocytes arise in the extravascular connective tissue. 
Their progenitor is indistinguishable from the large and medium- 
sized medullary lymphocytes. The mature eosinophils second- 
arily enter the vascular spaces, and continue their development 
during their passage into the peripheral circulation (compare 
fig. 49 with fig. 11). The first indication of the beginning of 
differentiation of a ‘lymphocyte’ into an eosinophilic myelo- 
cyte is the appearance of a few, very minute, purplish-red gran- 
ules (figs. 36 and 44). The first granules are most commonly 
aggregated in a certain restricted region, generally in the vicinity 
of the centrosome, and only gradually appear in all portions of 
the cytoplasm. They increase gradually in number and in size, 
always maintain a fairly uniform size for any particular stage 
(figs. 45 and 46), and during their later phases resemble those of 
the circulating eosinophils in that their centers are less dense, 
giving them the appearance of rings (figs. 47 to 50). The gran- 
ules apparently grow by a process of swelling involving, beside 
increase of diameter of the granules, a rarefaction especially of 
_the core, and a slight general decrease in staining capacity. 
The original eosinophilic granule has a purplish-red color, the 
definitive form a slightly orange-red color. This material gives 
no indication of the primitive basophilic granules described by 
Downey® for the eosinophilic myelocytes of the guinea-pig. 
Nor does either the developing or the definitive eosinophilic 
leucocyte contain intranuclear eosinophilic granules, as claimed 
