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Updated: May 4, 2025
It may here be noticed that, among the inferior animals with large nerves and more medullary substance, there are acuter senses; but man, excelling them in the general bulk of his brain, and more particularly in the cortical portion of it, has far superior powers of mind. These are circumstances that deserve the deepest consideration.
A nerve is a continuation of the medullary substance of the brain from the head or spine towards the other parts of the body, wrapped in its proper membrane. The muscular fibres are moving organs intermixed with that medullary substance, which is continued along the nerves, as mentioned above.
From the medullary substance proceed certain cords or prolongations, termed 'nerves', by which the animal is enabled to receive impressions from surrounding objects and to connect himself with them, and also to possess many pleasurable or painful sensations.
The age is easily determined; the pith rays, or medullary rays, are also plain. These form what is called the silver grain of the wood. The ducts, also, are clear in the Oak and Chestnut. There is a difference in color between the outer and inner wood, the older wood becomes darker and is called the heart-wood, the outer is the sap-wood.
According to Livingstone, the gorilla also "sits in pelting rain with his hands over his head." The points of convergence seem to stand in some relation to those points in the embryo which are last closed in during development. There appears, also, to exist some relation between the arrangement of the hair on the limbs, and the course of the medullary arteries.
There was less action of the liver than usually indicates a salvable case, and no irritation of the lowest intestines. Pari passu with the gastritic suffering, the neuralgic pain spread down the extremities from an apparent centre between the kidneys, through the trunk, from another line near the left margin of the liver, and through the whole medullary substance of the brain itself.
His theory of the action of his compound upon timber was briefly this: "That all wood before it can decay must ferment; that fermentation cannot exist without heat and moisture; that the chemical property or nature of his compound, when inserted dry into wood, is to attract moisture, and this moisture, aided by fermentation, liquefies the compound; that capillary attraction must inevitably convey it through the sap ducts and medullary rays to every fiber of the stick.... Were these crystallizations salt alone, they would soon dissolve, but the arsenic and corrosive sublimate have rendered them insoluble; hence they remain intact while any fiber of the wood is left."
Hence the formation of a medullary tube out of the outer skin takes place in the naked dorsal surface of the free-swimming larva of the Amphioxus in just the same way as we have found in the embryo of man and the higher animals within the foetal membranes.
"It is not on account of having written several works on the pathological anatomy of medullary lesions, and especially on the alterations of the spinal ganglia, that one acquires authority in a question so comprehensive and so delicate." "Do not be too modest, dear friend. I have had, lately, to consult my Dictionary of Medicine, and at each page your work was quoted.
This point is known as the node of Ranvier. These are known as the non-medullary fibers. They are gray, while the ordinary medullary fibers are white in appearance. The white nerve fibers form the white part of the brain and of the spinal cord, and the greater part of the cerebro-spinal nerves.
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