254 



ELEMENTS OF MAMMALIAN ANATOMY 



as in Ornithorhynchus. The above-mentioned features show 

 that the ornithodclphian brain presents a striking similarity to 

 the brains of reptiles and birds. The brains of Rodentia possess 

 but few convolutions, while the brain of man is the most highly 

 convoluted. 



The size of the brain varies widely. As a rule, the larger the 



brain in proportion to the size 

 of the animal, the greater is 

 its intelligence. However, in 

 man there appears to be but 

 slight connection between size 

 of brain and intelligence, as an 

 individual with a small brain 

 may be much more capable 

 mentally than one with a large 

 brain. Mental power in man 

 seems to depend upon the 

 development of the cells and 

 libers of the brain. 



The average weight of a male 

 human brain is about three 

 pounds; of a female, about two 

 and two-thirds pounds. The 

 human brain is J-^4 the weight 

 of the body; the ape's, J^g; the 

 rat's, J^2; the sheep's, 1^51; 

 and the elephant's, ^500- The brain of man is larger than 

 that of any other mammal except the whale and elephant. 

 The brain of a large whale weighs over four pounds, while that 

 of a large elephant will weigh about ten pounds. 



LABORATORY STUDIES AND SUGGESTIONS 



1. How many nerves transmit the stimuli received by the organs of special 

 sense? 



2. Where are the sense organs of pain located? 



Fig. 123. — Brain of the Rabbit 

 FROM Dorsal Aspect. 



