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Updated: May 4, 2025
Prentiss, in Science, October 3, 1890, has collected numerous instances of sudden canities, several of which will be given: "In the Canada Journal of Medical Science, 1882, p. 113, is reported a case of sudden canities due to business-worry. The microscope showed a great many air-vesicles both in the medullary substance and between the medullary and cortical substance.
We have, therefore, to examine the features of the psychic organ in man. The reader already knows the incontestable answer to this question. Man's psychic organ is, in structure and origin, just the same organ as in all the other Vertebrates. It originates in the shape of a simple medullary tube from the outer membrane of the embryo the skin-sense layer.
This formation of new bone is much in excess of the normal, the bones become large and bulky, their surfaces rough and uneven, their texture sclerosed in parts, and the medullary canal is frequently obliterated. These changes are well brought out in X-ray photographs. [Illustration: FIG.
This is certain, that it is in the head, since the head is the seat where the understanding thinks, and the will intends; and in front in the face of the head are man's five sensories, receiving life from the soul alone which resides in the head; but in what particular part of the head the soul has its more immediate residence, I dare not take upon me to say; yet I agree with those who fix its abode in the three ventricles of the brain, sometimes inclining to the opinion of those who fix it in the corpora striata therein, sometimes to theirs who fix it in the medullary substance of each brain, sometimes to theirs who fix it in the cortical substance, and sometimes to theirs who fix it in the dura mater; for arguments, and those too of weight, have not been wanting in the support of each of these opinions.
The chief occurrence on the second day of development is the construction of the two permanent openings of the gut the mouth and anus. In the earlier stages the alimentary tube is found to be entirely closed, after the closing of the primitive mouth; it only communicates behind by the neurenteric canal with the medullary tube. The permanent mouth is a secondary formation, at the opposite end.
The simple cerebral vesicle that is formed by the expansion of the head-part of this medullary tube divides by transverse constrictions into five, and these pass through more or less the same stages of construction in the human embryo as in the rest of the mammals. As these are undoubtedly of a common origin, their brain and spinal cord must also have a common origin.
They do not begin to diverge until after the medullary tube and alimentary canal, and the axial rod with the muscles between the two, have been formed. The Amphioxus continues to advance, and resembles the embryonic forms of the higher vertebrates; the Ascidia degenerates more and more, and at last, in its adult condition, has the appearance of a very imperfect invertebrate.
Brute strength seems to be the character of the former, and superior intelligence of the latter. There is, comparing bulk with bulk, less of the medullary substance in the horse than in the ox and in the dog than in the horse and they are characterized as the sluggish ox, the intelligent horse, and the intellectual and companionable dog.
The medullary substance of the brain displays but a feeble analogy with the albuminous and gelatinous matter of the electric organs. But these two substances have in common the great quantity of arterial blood which they receive, and which is deoxidated in them.
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