A treatise on physiology and hygiene for educational institutions and general readers .. . ngata., or oblong marrow. 7. The tissue of the brain is soft and easily altered in shape bypressure; it therefore requires to be placed in a well-protected position,such as is afforded by the skull, or cranium, which is strong with-out being cumbrous. In the course of an ordinary lifetime, this bonybox sustains many blows with little inconvenience ; while, if theyfell directly upon the brain, they would at once, and completely,disorganize that structure. Within the skull, the brain is envelopedby certain
A treatise on physiology and hygiene for educational institutions and general readers .. . ngata., or oblong marrow. 7. The tissue of the brain is soft and easily altered in shape bypressure; it therefore requires to be placed in a well-protected position,such as is afforded by the skull, or cranium, which is strong with-out being cumbrous. In the course of an ordinary lifetime, this bonybox sustains many blows with little inconvenience ; while, if theyfell directly upon the brain, they would at once, and completely,disorganize that structure. Within the skull, the brain is envelopedby certain membranes, which at once protect it from friction andfurnish it with a supply of nutrient vessels; they are called thearachnoid, or spiders web, the dura mater, and the pia mater, orthe tough and delicate coverings. The supply of blood sent 6. Location of the brain ? Its weight? Its shape? Of what it consists? What organsat the base? 7. The tissue of the brain ? What, therefore, is required? Blows on the head? Mem-branes of the brain ? Blood sent to the br^in ? 184 THE NERVOUS Fig. 48.—The Cerebrospinal System. THE NERVOUS SYSTEM. 185 to the brain is very liberal, amounting to one-fifth of all that, theentire body possesses. The brain of man is heavier than that ofany other animal, except the elephant and whale. 8. The Cerebrum.—The brain proper, or cerebrum, is thelargest of the intracranial organs, and occupies the entire upper andfront portion of the skull. It is almost completely bisected by afissure, or cleft, running through it lengthwise, into two equal partscalled hemispheres. The exterior of these hemispheres is gray incolor, consisting chiefly of nerve-cells, arranged so as to form a layerof gray matter one-fifth of an inch in thickness, and is abundantlysupplied with blood-vessels. The interior of the brain, however, iscomposed almost wholly of white substance, or nerve-fibres. 9. The surface of thecerebrum is divided by aconsiderable number ofwinding a
Size: 1241px × 2014px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1, booksubjectphysiology, bookyear1887
