198 ME. F. E. BEDDAED— CONTEIBUTIONS TO THE 



trate a point of this sort in an animal which cannot be readily examined by a person 

 who is treating of the subject of the palatal rugte. 



§ 10. The Brain. 



I have compared the brain of the Bald-headed Chimpanzee with the brains of two 

 Common Chimpanzees ; the latter, however, naturally presented some ditferences from 

 each other, which rendered the task of comparison more difficult. 



The brain of "Sally" weighed, after removal of the pia mater and after an immersion 

 of four months in spirit, 8f oz, ; it had been allowed to dry for about an hour and a 

 half before weighing ; it was then damp but not wet. 



The two other Chimpanzees' brains were weighed under the same conditions ^, and 

 were found to weigh respectively Q^ oz. and 6f oz. 



These two Chimpanzees were of about the same size, and not much more than half 

 the size of " Sally." They were both a little larger (about 4 or 5 inches taller) than the 

 animal examined by Dr. Symington ^, the brain of which weighed under pretty much 

 the same conditions 8^ oz. I cannot account for the very great difference ; it prevents 

 me from attempting to draw any conclusions as to the weight of the brain in Troglo- 

 dytes calvus. 



The brain of Troglodytes calvus is deeper in proportion to its length than either of 

 the two brains of Troglodytes niger with which I compared it. 



The lengths of the brain as compared with their height are as follows : — 



Length. Height, 



mm. mm. 



Troglodytes calvus 108 65 



niger (a) 100 58 



niger (b) 102 62 ^ 



The measurements are taken by placing vertical plates beside the brain, and are 

 therefore only true as regards the proportions. 



The actual measurements of the brain of Troglodytes calvus are as follows : — 

 Length lOo mm., brea,dth 80 mm., height 62 mm. 



In viewing the cerebrum from the upper surface (Plate XXIII. fig. 3), the most 

 striking difference between the two species was the condition of the parieto-occipital 

 fissure (the " Simian fissure," as it has been called). In Man this fissure is of small 



' One of them has been eight months, the other ten months in spirit. 



^ " On the Viscera of a Female Chimpanzee," Proc. Eoy. Phys. Soc. Edinb. vol. x. p. 300. 

 In this Chimpanzee the temporo-sphenoidal lobes projected downwards in a much more marked degree 

 than in the other. The vertical diameter of the brain was naturally increased thereby ; 5 or 6 mm. must be 

 allowed for this difference. 



