232 



CHESTER H. HEUSER 



is difficult to establish lines whose loci will be absolutely com- 

 parable throughout the series. The apex of the angle has been 

 located in the middle point of the mid-brain ventricle; one line 

 has been drawn from it to the optic recess, and the other to the 

 middle point in the cavity of the central canal opposite the 

 cervical bend 



Fig. 1 Outline from figure 5, showing the position of the mid-brain angle 



TABLE 3 

 Increase in the mid-hrain angle 



The angle increases from 30° in the 5.1-mm. embryo to 152° in 

 the adult. The curve of growth of this angle rises up relatively 

 rapidly at first and slowly in later stages to the adult. 



CONCLUSIONS 



The well-known series of models of the developing human 

 brain made by His and the papers which they illustrate make 

 it possible to compare the conditions which have been described 

 in the pig with those in man. Comparisons with the embryonic 

 brain of other mammals cannot be made, since it appears that 

 no one has attempted to extend the work of His here referred 

 to, or even to repeat it critically. The first impression derived 



