466 H. E. JORDAN 
the rounding up of an irregular, generally stellate cell (fig. 33), 
and a condensation and increase in basophily of the cytoplasm 
(fig. 34). The nuclei of the typical mesenchymal cells and the 
derived hemoblasts are practically identical. These nuclei are 
of a vesicular lightly-staining character, with a pale nucleolus, 
several deeply chromatic karyosomes, and many very minute 
chromatic granules scattered among a very delicate chromatic 
reticulum. This description fits also the smaller types of hemo- 
_blasts, both intra- and extravascular. In general, further dif- 
ferentiation into the various types of blood-cells involves first an 
increase in the number of larger, more regular karyosomes, so that 
the nucleus has a coarsely granular appearance, many granules 
lying peripherally upon the more robust, chromatic, nuclear 
membrane. ‘The plasmosome meanwhile persists. Later stages 
are characterized mainly by increase in the general chromaticity 
of the nuclear sap, giving the entire nucleus, now with a coarser 
reticulum, a deep blue coloration. Only the larger lympho- 
cytes divide mitotically; the smaller lymphocytes do not divide 
as such; they may grow to larger size and then divide mitotically. 
Excessive growth of the large lymphocytes leads to giant-cells 
(fig. 73). Both neutrophilic and eosinophilic leucocytes also 
divide mitotically during their earlier stages, while the nucleus 
remains of spheroidal shape. Similarly, young spheroidal eryth- 
roblasts may divide mitotically within the blood-vessels. 
Neither basophilic leucocytes nor thrombocytes were seen in 
either mitosis or amitosis. 
Besides proliferation by mitosis, large lymphocytes, young 
erythroblasts, and young neutrophilic leucocytes also divide 
amitotically. What determines whether a lymphocyte or eryth- 
roblast shall divide directly or indirectly remains obscure; 
possibly the two modes of division are determined by divergent 
metabolic conditions as expressed in the nucleo-cytoplasmic 
relationship. However, the amitotic division of the neutro- 
philic leucocytes, of which the extreme lobulation of the later 
nucleus must probably be reckoned a phase, is the more surpris- 
ing, since here an astral system is maintained intact and is at all 
stages conspicuous. Possibly here the mitotic incapacity of the 
