Page:The Galaxy, Volume 6.djvu/52

42 brains are to be found the rabbit, the guinea pig, the sloth, the mole, the kangaroo, the opossum, and that paradoxical being, the ornithorhynchus. None of the birds, reptiles, or fish have convoluted brains.

Professor Richard Owen, in his work on the classification and geographical distribution of the mammalia, proposes to divide them into four groups; the typical characteristic of each being the degree of development attained by the brain. Two of these groups have smooth brains; in the other two this organ is convoluted. There are certain objections to this arrangement which it is not necessary to consider now, and the circumstance is only mentioned in order that the reader may know that one of the most eminent comparative anatomists of the age attaches very great importance to these convolutions. In fact, it is generally admitted by physiologists that the amount of intelligence possessed by animals is directly proportional to the quantity of gray matter found in their brains, and to the number, extent, and general complexity of the cerebral convolutions. Not only is this true as regards the several genera and species, but it is equally true as regards individuals of any species. In man great differences have been observed in this respect. The brains of idiots are found either to have very few convolutions, or else they are slightly marked, while in persons remarkable for mental vigor the convolutions are numerous and strongly indicated. In the brain of an idiot which the writer examined a few years since, the convolutions were exceedingly sparse and superficial, and the gray matter, instead of being of the normal thickness of about the eight of an inch, was scarcely thicker than a sheet of paper, and in some parts could scarcely be distinguished at all. The gray matter on the surface of Daniel Webster's brain, was three-sixteenths of an inch thick, and the depth of the spaces between the convolutions was on the vertex seven-eighths of an inch. As the gray matter covers the convolutions throughout all their ramifications, Mr. Webster's brain must necessarily have contained a large amount of it.

One other element requires consideration in our determination of the intelligence of animals, and that is the size of the brain. This, however, is so much modified by the very important element of quality, that no absolute rule can be laid down. In general, however, other things being equal, the intellectual develmentdevelopment [sic] is directly proportional to the quantity of brain-substance.

The researches of European observers give 49 1-2 ounces as the weight of the average brain of the white inhabitant of Europe, the maximum, that of Cuvier, being 64 1-3 ounces, and the minimum consistent with fair intelligence, 34 ounces. Webster's brain (allowance being made for disease which existed) weighed 63 3-4 ounces; Dr. Abercrombie's 63 ounces, and Spurzheim's 55 1-16 ounces. The average of 24 white American brains, accurately weighed by Dr. Ira Russell, was 52.06 ounces; the maximum 64, and the minimum 44 1-4. The same observer found the average full negro brain, as determined from 147 specimens, to be but 46.96 ounces.

The capacity of Daniel Webster's cranium was the largest on record, being 122 cubic inches. That of the Teutonic family, including English, Germans, and Americans, is 92 cubic inches. In the native African negro it is 83 cubic inches; and in the Australian and Hottentot, but 75. The brain of the idiot seldom weighs over 23 ounces, and is often much less than this. In the instance already referred to as coming under the writer's notice, the weight of the entire brain was but 14 1-2 ounces. Mr. Gore has related in the "Anthropological Review," the particulars of a case of microcephaly in which the brain weighed but