302 Froceedings of the Royal Physical Society. 



brain. Viewed from the norma verticalis,. the total length of 

 the cerebrum was 95 mm., and the distance from the anterior 

 end of the brain to the upper extremity of the fissure was 



Fig. 1. 



Left lialf of vertical mesial section of brain of chimpanzee, c. c. , Corpus 



callosum. c. m., Calloso-marginal fissure, p. o., Parieto-occipital fissure, 



c. , Calcarine fissure, p., Pons Varolii, m. o., Medulla, m., Middle 

 commissure of third ventricle. 



59 mm. Calculated according to the method adopted by 

 Marshall, this gives an index of 62, showing the fissure to be 

 even farther back than in man, in whom it is estimated 

 at 57. 



Gratiolet, in his " Memoire sur les plis cerebraux de 

 Thomme et des primates," has a view from above of the brain 

 of a chimpanzee {see plate vi., fig. 1). I find that this 

 agrees very closely with my own specimen in regard to the 

 position of the fissure of Eolando, as it gives an index of 60°. 

 It must be remembered that these indices are only approxi- 

 mate estimates of the position of the fissure as seen from 

 above, since they are readily influenced by the position of the 

 brain. Thus in my specimen a rotation of the brain round 



