The Cerebrum forms the largest portion of the encephalic mass, and occupies a considerable part of the cavity v of the cranium, resting in the anterior and middle fossae of the base of the skull, and separated posteriorly from the cerebellum by the tentorium cerebelli. About the middle of its under surface is a narrow constricted portion, part of which, the crura cerebri, is continued onwards into the pons Varolii below, and through it to the medulla oblongata and spinal cord; whilst another portion, the crura cerebelli, pass down into the cerebellum.

  The Cerebellum (little brain or after brain) is situated in the inferior occipital fossa;, being separated from the under surface of the posterior lobes of the cerebrum by the tentorium cerebelli. It is connected to the rest of the encephalic mass by means of connecting bands, called crura; of these, two ascend to the cerebrum, two descend to the medulla oblongata, and two blend together in front, forming the pons Varolii.

  The Pons Varolii is that portion of the encephalic mass which rests upon the upper part of the basilar process. It constitutes a sort of centre to the various segments above named, receiving, above, the crura from the cerebrum; at the sides, the crura from the cerebellum; and, being connected, below, with the medulla oblongata.

  The Medulla Oblongata extends from the lower border of the pons Varolii to the upper part of the spinal cord. It lies beneath the cerebellum, resting on the lower part of the basilar groove of the occipital bone.

  Weight of the Encephalon. The average weight of the brain in the adult male is 49,05oz., or a little more than 3 Ib. avoirdupois, that of the female 44 oz., the average difference between the two being from 5 to 6 oz. The prevailing weight of the brain in the male ranges between 46 oz, and 53 oz., and in the female, between 41 oz. and 47 oz. In the male, the maximum weight out of 278 cases was 65 oz., and the minimum weight 34oz. The maximum weight of the adult female brain, out of 191 cases, was 56oz., and the minimum weight 31 oz. It appears that the weight of the brain increases rapidly up to the seventh year, more slowly to between sixteen and twenty, and still more slowly to between thirty and forty, when it reaches its maximum. Beyond this period, as age advances and the mental faculties decline, the brain diminishes slowly in weight about an ounce for each subsequent decennial period. These results apply alike to both sexes.

  The size of the brain appears to bear a general relation to the intellectual capacity of the individual. Cuvier's brain weighed rather more than 64 oz., that of the late Dr. Abercrombie 63 oz., and that of Dupuytren 62,05oz. On the other hand, the brain of an idiot seldom weighs more than 23 oz.

  The human brain is heavier than that of all the lower animals excepting the elephant and whale. The brain of the former weighs from 8 Ib. to 10lb., and that of the whale, in a specimen seventy-five feet long, weighed rather more than 5 Ib.