The human brain is the most important organ which distinguishes man from animals. The brain is the center of all mental activities. Through the brain man discovers what is going on in the world about him and determines his own attitude toward the world. All the evidence of man’s senses is brought to the brain. The brain receives what the eyes sees, the nose smells, the tongue tastes, the ear hears, and the skin feels. In the brain man stores up his memories of the past.

The brain has often been compared with a huge telephone switchboard, but no telephone system could hope to equal the vast number of brain connections. There are millions upon millions of connections between the various cells which make up the brain.

The average human brain weighs a little over three pounds. The male brain weighs a few ounces more than the female brain. The largest human brains have weighed almost four pounds. The size of the brain in most cases seems to have no direct bearing upon intelligence. Some great geniuses have had large brains, others have had smaller brains. Idiots have been known to possess large brains. With two exceptions, man has the largest brain in the world. Both the whale and the elephant have larger brains, but their brains are not as large in proportion to their total weight as man’s brain is. Man’s brain weighs about one fortieth, or a little less, of his total body weight.