STUDIEN ÜBER DIE CEREBRALISATION: ZUR QUANTITATIVEN BESTIMMUNG DER RANGORDNUNG BEI SÄUGETIEREN

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Abstract
The value of the exponent r in the Dubois formula e = csr was calculated from the wts. of fresh brains of mammals. The wts. of different parts of the brain were considered because they perform different functions and since their wts. are variable. The wts. of the integrating centers (neopallium, cerebellum, olfactory lobes) were plotted against the brain stem which is vegetative in function. The data were plotted on a logarithmic grid and the pitch of the straight lines were calculated by the usual method of linear regression; the values of these exponents are measures of the slopes of the lines. No constant values such as were maintained by Dubois were found. The degree of cerebralization was found by plotting the wts. of the parts against a basic measure which ensures adjustment for unequal body wts. Such indices permit separation of the animals into 3 groups low rank, middle rank, and high rank. Each of these has a separate rank of cerebralization. The neopallial indices confirm this order almost without exception. The neopallial values not only become progressively greater, but their percentage of the entire brain also increases. The neopallial index is the best criterion for determining the degree of cerebralization. The olfactory indices vary greatly. Grossly, the rhinencephalon, is largest in Insectivora and Dasypus; decreases gradually in Rodentia, Carnivora, and Ungulata, and practically disappears in Primates and aquatic mammals. The cerebellum is nearly constant. The degree of cerebralization is a measure of centralization (in the sense of Franz, 1935).

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