The brain is shown from above downwards and from fore and aft. The two hemispheres from above downwards resemble an English walnut, excepting that the convolutions are not the same. The convolutions are indicated where the gray matter dips down into the. white matter in folds. The cross-section shows how that dipping occurs and indicates roughly how the fibres run. While the weight of the entire brain is only about one fortysecond of the weight of the entire body, it has been calculated (After Edinger.) that the supply of blood is one-eighth of

CUT No. 21.

that used by the whole body. How essential this supply of blood is becomes evident if it is in any way interfered with. Stop any one of the great arteries leading to the brain and consciousness is at once dissipated. Dr. Lombard found that the temperature varies rapidly, though slightly, during waking hours. He found that a noise or anything that attracted attention would. produce an elevation of temperature. The rise of temperature is also produced by thought or emotion. Mosso, the Italian investigator, found, with careful balances, that the weight of the head increased in direct proportion to the profundity of thought, showing that the blood flows more rapidly to the brain when one is thinking.

Weight of the Brain.

M. Mathiega, an anthropologist of Prague, has settled by experiment beyond doubt the long asserted fact that the weight of the brain of educated persons is greater than that of the common crowd. He took the brains of 235 persons between the ages of 20 and 60 years, of varying occupations and intellectual culture, and found that the brain of the day laborer

weighed 1,400 grammes; workmen and unskilled laborers, 1,423; porters, guardians and watchers, 1,436; mechanics, 1,450; business men and photographers' assistants, 1,468, and physicians and professors, 1,500.

These statistics show that the weight of the brain increases in gradual progression. True also is the fact that the sale of alcoholic drinks is not conducive to cerebral development, as shown by the light weight of the brains of brewers, beer-shop keepers, and waiters.

Madison C. Peters says: "The number of bones in the human body is variously estimated, say, two hundred and forty (the bones vary in different periods of life, several, separated in youth, being united in old age); these bones have forty distinct indentations, four hundred and forty-six muscles within, so that the bones and muscles have upwards of fourteen thousand indentations. There are not less than ten thousand nerves, with an equal number of veins and arteries, one thousand ligaments, four thousand lacteals and lymphatics, one hundred thousand glands, and the skin contains not less than two hundred millions of pores, all of which are so many avenues of health or sickness, life or death.

"The heart, about ten ounces in weight, contracts about four thousand times every hour, and through it during that period passes two hundred and fifty pounds of blood, while within the compass of a day it makes more than one hundred thousand pulsations and in a year more than thirty-six millions; it performs more than one-fifth of the mechanical work of the body, exerting a force that would lift its own weight 13,000 feet every hour."

Neurones or Nerve Fibres.

It would be hopeless to try to describe the practical infinitude of the nerve cells or neurones that transmit stimuli here and there. Even if we knew the exact arrangement of each neurone in a man's brain, it would take a model as large as S. Paul's Cathedral to make them visible to the naked eye. Consider that, counting at the rate of fifty a minute, it would take a man working twelve hours every day over two hundred years merely to count the nerve cells of one man. Dr. Thorn

dike's latest figures are that the nerves, as estimated, number three thousand millions of neurones.

(Kölliker.)

"Each of these is itself a complex organ, and is often capable of many connections. Since it would take three lifetimes to merely count the neurones and probably the lifetimes of three Melchisedecs to count their connections, it is evident that the brain is complicated enough to register the richest and most active human experience."

An individual nerve cell is now shown. There is seen the cell body, the nucleus and some of the many branches. Generally speaking, the cell bodies are placed towards the surface of the spinal cord and the cortex of the brain, and the fibres hang downwards. The grey matter is really caused by the mass of the dark cell bodies, while the white matter is the fibres.

If the brain cells were all placed on the same plane. we would get a diagrammatic scheme like the following; but as they

are not on the same plane, we really secure a picture like this one shown. (Cut 24.)

It is as if we were to drive a cleaver through a basket of apples: one would be cut through the skin, another through the stem, another one would be shaved off at the lower end, the fourth would be cut through the centre one way, and the fifth through the centre another way, and the sixth half-way between. So that we would really get all shapes in our sections. Cell bodies are embodied in the general mass of the brain cortex, or rather of the margin of the spinal cord as it has been wound around in the spiral evolution of the brain. Looking again at the diagrammatic scheme of the connection of the brain cells, it will be seen that any cell theoretically can reach any other cell. Theoretically speaking you can go to any local country telegraph office and reach any other station in the entire world. Potentially you are in connection with the world. So potentially any cell of the body of any kind can be reached by sending currents from any other cell. You can almost direct your blood by your mental power to any portion of the body. The impressions from the most remote section are received promptly through our nervous telephone system at headquarters, acted upon, and the corresponding command or judgment telephoned back to the sending section.

Individual nerve fibres are shown, indicating the Insulating Sheath, the Medulla and the Nodes (Nodes of Ranvier). Each section of a nerve is called a neurone. We see a direct analogy in our present telegraph and telephone systems, under which we have our wires with their insulation and the relay stations at every little distance. (Cut 25.)

CUT No. 25. Diagram Showing Neurone Connections. (Smith.)