. Advances in the study of mammalian behavior. Mammals. Structure, Development, and Function 123 3 - 2 - I - H= Homo sapiens. V- Cetaceans Carnivores Marsupials Log brain volume, E (ml.) Fig. 4. Length of "external" gyri and brain size. "External" gyri are those visible at the surface of the undissected brain and correspond to gyri visible in fossil endo- casts. (Data from Elias and Schwartz, 1971; graph modified from Jerison, 1982, copyright Plenum Press, New York.) answers for the questions in the first paragraph of this section. The external envelope of the cerebral cort
. Advances in the study of mammalian behavior. Mammals. Structure, Development, and Function 123 3 - 2 - I - H= Homo sapiens. V- Cetaceans Carnivores Marsupials Log brain volume, E (ml.) Fig. 4. Length of "external" gyri and brain size. "External" gyri are those visible at the surface of the undissected brain and correspond to gyri visible in fossil endo- casts. (Data from Elias and Schwartz, 1971; graph modified from Jerison, 1982, copyright Plenum Press, New York.) answers for the questions in the first paragraph of this section. The external envelope of the cerebral cortex and brain in mammals is fairly similar in shape in different species, and the surface of that envelope is related to brain size more or less according to Eq. 2 (with a suitable value for K). The regression of the length of the external gyri G versus brain size, presented in Fig. 4, is: G - £^<' (4) The area of the external surface of the cerebral cortex is the product of the length of the gyri and their average width. A dimensional analysis of the relationship between Eq. 4 and Eq. 2, therefore, suggests that the average width of the external gyri is approximately constant. If we treat Eq. 4 as exact, then the average width would be proportional to the — power of brain size, which would imply that larger brains have slightly narrower gyri than do smaller brains. The negative exponent is probably an artifact of the manner in which the lengths were measured, however, and as a first approx- imation it is certainly correct to treat the average width of gyri W as a constant across species of mammals. Without further analysis, we also note that: Endocast surface = WG = f{K''') (5). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Eisenberg, John Frederick; Kleiman, Devra G; American Society of Mamm
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