NERVOUS SYSTEM. VERTEBRATA. 465 



IT would perhaps be more in keeping with the intention* of the 

 founder of this Museum, who brought together such specimens as 

 would throw any light upon the structure of Man, to briefly summarise 

 such facts revealed in studying this collection of Vertebrate brains as 

 help to explain the complicated anatomy of the human brain. 



The human brain is by no means the largest known to us. The 

 Elephant and the Great Whales possess much larger organs, and even 

 the extinct Sirenian Rhytina was provided with a bruin of larger 

 absolute dimensions than that of Man. In the case of these huge 

 animals the enormous mass of the brain is probably to be explained 

 by the fact that the increase in size of the surface of the body 

 necessitates a corresponding growth of the neopallium (to which the 

 great proportions are chiefly due), which is the ultimate receptive- 

 organ for sensory impressions. 



In the case of the human brain, however, the Anthropoid Apes 

 (which approach near to Man in bodily dimensions) afford us a criterion 

 as to the amount of neopallium which may be regarded as " necessary " 

 (in the Family Simiidae) for the reception of impressions coming from 

 such an extent of sensory surface as Man possesses. When it is 

 remembered that the largest Ape's brain is approximately half the size 

 of the smallest normal human brain, and the average Gorilla's brain 

 only about one third (approximately) the weight of the average 

 European's brain, it will then be understood how great an area of 

 neopallium (to which the disproportionate size of the human and 

 Anthropoid brains is chiefly due) Man possesses over and above the 

 needs of the average member of the Simiidae, to serve as the physical 

 basis (so to speak) of an associative memory of immeasurably greater 

 potentialities (for storing and comparing sensory impressions) than 

 that of any other animal. The feature, therefore, which distinguishes 

 the human from all other brains is the relatively enormous size of the 

 neopallium in comparison with the minimum which the forces of 

 natural selection have made a condition of survival in a member of 

 the Simiidae *. 



The neopallium assumes important functions and becomes a condition 

 of survival for the first time in the Mammalia, and in each successive 

 epoch it has become incumbent upon every mammal either, on the 

 one hand, to adopt some eminently safe mode of life or some special 

 protective apparatus to avoid extinction, or, on the other hand, to 

 " cultivate " a larger neopallium, which, as the organ of associative 



* I use the term " neopallium" (Journ. Anat. and Phys. vol. xxxv. 1901, 

 p. 431) because the other parts of the pallium, . e. the hippocampus and 

 pyriform lobe, do not share in this increase. 



VOL. II. ^ H 



