CEREBRAL VENTRICLES IN THE PIG 



231 



TABLE 1 



Volume of the cerebral ventricles in cubic millimeters 



From table 1 it is seen that each part of the entire ventricular 

 system increases in size continually during development. The 

 increase is relatively greater at first, and as would be expected, 

 it becomes gradually less toward the adult. For a time — until 

 embryos measure between 12 and 20 mm. — the fourth ventricle 

 is the largest part of the ventricular sj^stem. After the lateral 

 ventricles have expanded appreciably the cavity of the fore-brain 

 is the largest part. 



The cross-sectional area of the interventricular foramen was 

 determined from wax models by measuring the area of the fora- 

 men cut through the narrowest portion. 



The cross-sectional area of the interventricular foramen be- 

 comes progressively greater up to about the 12-mm. stage after 

 which it becomes both relatively and absolutely smaller for some 

 time. In later stages it again expands considerably; in the 

 adult it is very much larger than in younger stages. 



TABLE 2 

 Area of the foramen interventriculare 



The mid-brain angle in early stages is very acute. For meas- 

 uring the angle in the different embryos during development it 



