120 SUPPLEMENTAL HISTORY OF MAN. 



medulla oblongata, and spinalis. To this, however, 

 one striking exception is to be found in the dolphin, 

 which seems to overturn any hypothesis built upon 

 these proportions. 



The deepest and most numerous convolutions 

 characterize the brain of man. This is apparently 

 in consequence of its size, and intended to afford a 

 more extensive surface for that vascular membrane, 

 the pia mater. 



As the brain of animals diminishes in size these 

 convolutions become shallower and fewer in number; 

 and in many animals do not exist at all. 



The greatest quantity of medullary substance in 

 proportion to the cortical belongs to the human brain, 

 and this proportion of medulla is much greater in 

 the adult than in the foetus. 



According to Soemmering the acervulus pinealis, 

 or pineal gland, constructed of a sandy or earthy 

 material, is peculiar to the healthy state of the human 

 brain, being found there from the fourteenth year. 

 It may be considered as almost confined to man, 

 but one instance has been recorded by himself, and 

 another by Malacarne of its occurrence in the fallow 

 deer and the goat. Its deficiency in the brain of 

 the human subject is considered by Blumenbach as 

 a very singular irregularity of structure : but the 

 Wenzels have ascertained that this deficiency is not 

 so uncommon as had been represented, and also that 

 the fourteenth year is not invariably the earliest date 

 of its appearance. 



Considerable changes take place in the human 



