Figs. 12 to 22. Camera lucida drawings of portions of tissue in cord and cere- 
brum chosen to show dividing cells. All the drawings were made with the Zeiss 
2mm. oil immersion lens and No. 6 eye-piece, tube length 176 mm. The drawings 
have been uniformly reduced to make the magnification as printed equal 800 diam- 
eters. The letters indicate the same structures throughout: mli, membrana 
limitans interna; g, dividing cell in germinal layer; mn, dividing cell in mantle 
(middle nuclear) layer; ep, ependymal cells; dt, cells in differentiated tissue; leu, 
leucocytes; ca, cell of capillary wall. 
Fig. 12 Four-day rat, cervical cord; dividing cell in germinal layer. > 800. 
Fig. 13 Six-day thoracic cord; large dividing cell in posterior horn. This cell 
is one of two dividing cells very near each other, each of which showed its chomo- 
somes in three consecutive sections of 8 micraeach. > 800. 
Fig. 14 Twelve-day thoracic cord; small dividing cell in posterior horn. 800. 
Fig. 15 Twelve-day thoracic cord; mesodermal dividing cell of capillary found 
in postero-lateral tract; same section as figure 14. 800. 
Fig. 16 Six-day cerebrum, cortex; leucocyte within a cross section of capillary 
and a dividing cell. It is difficult to determine whether the granular mass about 
the nucleus of the leucocyte is its cytoplasm or other material. > 800. 
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