A manual of anatomy . the eighteenth or twentieth year. The brain beginsto lose weight after the sixtieth year and very rapidly from seventyto eighty years. The important/oc/or^ that affect brain weight areage, sex, race, intelligence, skull form and body weight. In regard to race the Caucasians have the heaviest and the Aus-tralians the lightest. There is considerable variation in the Cau- THE BRAIN 371 casian race. In regard to intelligence, the brains of the highly in-tellectual individuals will weigh on the average 100 grams weighing under 1000 grams in the male and 900 grams i
A manual of anatomy . the eighteenth or twentieth year. The brain beginsto lose weight after the sixtieth year and very rapidly from seventyto eighty years. The important/oc/or^ that affect brain weight areage, sex, race, intelligence, skull form and body weight. In regard to race the Caucasians have the heaviest and the Aus-tralians the lightest. There is considerable variation in the Cau- THE BRAIN 371 casian race. In regard to intelligence, the brains of the highly in-tellectual individuals will weigh on the average 100 grams weighing under 1000 grams in the male and 900 grams in thefemale are usually considered too low for mental integrity. The brain consists of a number of divisions: (i) the cerebrum,comprising the cerebral hemispheres and a number of lesser structures;second, the cerebellum; third, the brain stem, comprising the midbrain,the pons and tegmental portion and the oblongata. The brain as awhole when viewed from above, exhibits two lateral masses, the henii- Optic nerve Hypophy. Glossopharyn-geal andvagal nerves Hypoglossal nerve Facial nerve Auditory nerve Fig. 263.—Ventral aspect of the brain showing the attachment of the cerebral nerves. {From a pholosrapli.) spheres, separated by a deep cleft, the longitudinal fissure (fissiiralongitudinalis cerebri). The frontal pole is rather narrow but notpointed. The parietooccipital region in the broadest and mostmassive, while the occipital pole is rather sharply pointed. Thesuperior and lateral surfaces show several rather deep clefts or fissuresand a number of smaller clefts or sulci; these separate the variouslobes and convolutions from one another. The size and number ofthese convolutions depends upon the degree of intelligence. Whenthe hemispheres are separated a whitish band, quite extensive fronto-occipitally, is seen at the bottom of the fissure connecting the twohemispheres; this is the corpus callosum, or intercerebral cerebellum is not visible in this view. The under
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthumananatomy, bookyea
