THE NERVOUS SYSTEM. 229 
striking similarity to the brains of 
reptiles and birds. The brains of 
Rodentia possess but few convo- 
lutions, 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 this statement 
does not always hold true, as an indi- 
vidual with a small brain may be 
much more capable mentally than 
a ‘ Fic. 114. BRAIN OF THE 
one with a large brain. Mental Rappit FROM DORSAL 
power in man seems to depend upon SSEee 
the development of the cells and eee al aon 
fibers 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 44 the weight of the body; the ape’s, 
g'g; the rat’s, gx; the sheep’s, 34;; and the elephant’s, x4. 
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. 
PRACTICAL QUESTIONS 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? 
3. How many sense organs are visible in the mesentery of your 
specimen? 
4. Describe the path of a stimulus from the index finger to the brain. 
5. Through which nerve roots would the stimuli received by the 
cutaneous sense organs pass into the cord? 
6. Describe the nerves transmitting the stimuli from the olfactory 
organ. 
