,- • . - 







6 



1. Photomicrograph. Embryo 350 (/5 mm.). Cross-section 75 - I - 5. X 8 The cavum mediale corporis striali (c m) appears in symmetrical 



positions on the two sides of the brain. That on the right side is given at a higher magnification in Figure 2. 



2. Photomicrograph. Cavum mediale dextrum. X I44. The position is indicated in Figure I . 



3. Photomicrograoh. Embryo I44 (14 mm.). Sagittal section 4-1-2. X 5. The earliest appearance of the cavum laterale sinistrum (c/) 



is indicated here and illustrated at a higher magnification in Figure 4. 



4. Drawing of the cavum laterale corporis striati. X 500. Macrophages (m a) may be ■teen among the strands of protoplasm bridging the 



cavity, b v, blood-vessel The r>ns ; tion of this drawing is indicated in Figure 3. (Drawn by J. F. DiJinch.) 

 5 Photomicrograph. Embryo 43 ! (18.5 mm.). Sagittal section 12-1-1. X 7'<f. The very large cavum laterale sinistrum (c/) is 



shown in its relation to the nia mater and the ventricle of the brain A more highly magnified drawing is given in Figure 6. 

 b Drawing of the cavum laterale sinistrum. X '90 A single layer of nerve-cells separates the space from the pia mater (p m). Large 



numbers of macrophages (m a), a detailed drawing of which is given in Figure 12. are present Rlood-vessels (b v) traverse the cavity. 

 nded by a few nerve-cells. The position of this drawing is indicated in Figure 5. (Drawn hi/ J F. Didusch.) 



