A study of these equations shows at once the precise relation of each of the other characters, both singly and combined, to brain-weight. The equations afford a means of scientifically comparing the mean brain-weight of different races, since by their use we can, in effect, reduce the races to be compared to the same base with reference to other characters. This use of the equations is illustrated for a specific instance in Table I, supra. Numerous other uses to which they may be put are In using these equations the following points should be kept in mind: (a) The equations give the probable mean brain-weight of an array of given type in respect to other characters. They are therefore not to be depended on to predict individual brainweights. ble. (b) They are strictly intra racial equations. (c) The male and female equations are not interchangea (d) On material comprising individuals between the ages of 15 and 50 the equations based on the "young" series should be used. I I Concluding Remarks. In concluding I desire to call attention to the following points. (a) The essential agreement between the four different races studied in respect to the biometric constants for variation and correlation in brain-weight is noteworthy. This agreement in the statistical constants from four series of data so divergent in their origin as those treated in this work cannot reasonably be held to be fortuitous. It can only mean that there are definite laws underlying variation in the weight of the brain which are not fundamentally different from the laws of variation for the other characters of the body. (b) There is no evidence that intellectual ability and the weight of the brain are in any degree correlated in normal individuals. ( There is need for more and larger collections of brainweighings, in which close attention is paid to the homogeneity of the material, and to the recording of other subsidiary data in addition to brain-weight. In comparison with the series of brain-weighings available at present, a collection which should record the following facts would be almost ideal. I. Brain-weight, by the standard method. 2. Race. In this the more essential detail given the better. 3. Country of residence during adult life. This list is presented with the hope that any future worker who may be about to undertake the labor involved in obtaining a large mass of human brain weight statistics will at least consider the points raised. It gives me pleasure to acknowledge my indebtedness to the Carnegie Institution for aid in carrying on this and other biometric investigations. LITERATURE CITED. Beeton, M. and Pearson, K. :01. Inheritance of the Duration of Life and the Intensity of Natural Selection in Man. Biometrika, Vol. 1, pp. 50-89. 1901. Bischoff, T. L. W. v. '80. Das Hirngewicht des Menschen. Bonn, 1880, pp. vi and 171, plus Tables. Deniker, :00. The Races of Man. London and New York, 1900, pp. xxiii and 611. Fawcett, C. D. :02. A Second Study of the Variation and Correlation of the Human Skull, with Special Reference to the Naqada Crania. Biometrika, Vol. I, pp. 408-467 Pl. IV-X, Tables 1-8, 1902. Greenwood, M. :04. A First Study of the Weight, Variability and Correlation of the Human Lee, A. and Pearson, K. :01. Data for the Problem of Evolution in Man. VI. A First Study of the 1901. Macdonell, W. R. :04. A Study of the Variation and Correlation of the Human Skull, with Specia] Marchand, :02. Ueber das Hirngewicht des Menschen. Abhandl. d. math.-phys. Cl. d. Königl. Sächs. Gesellsch. d. Wiss. Bd. XXVII, No. IV, pp. 393-482. 1902. Matiegka, H, :03. Ueber das Hirngewicht, die Schädelkapacität und die Kopfform, sowie deren Beziehungen zur psychischen Thätigkeit des Menschen. Sitz. ber. der kön. böhmischen Gesellsch. d. Wissensch. Mathem.-Naturwiss. Classe. Jahrg. 1902. No. XX, pp. 1-75. Pearson, K. '97. The Chances of Death. Vol. I, London and New York, 1897, pp. ix and 388. Retzius, G. :00. Ueber das Hirngewicht der Schweden. Biol. Untersuchungen, N. F. Ripley, W. Z. '99. The Races of Europe. New York, 1899, pp. xxxii and 624. THE RELATION BETWEEN THE OCCURRENCE OF WHITE RAMI FIBERS AND THE SPINAL ACCESSORY NERVE. By A. H. ROтн, A.B., M.D., Instructor of Anatomy in the University of Michigan. (With an Addendum by J. PLAYFAIR MCMURRICH) With One Figure. In two important papers published in 1886 and 1889 GASKELL pointed out that the spinal accessory nerve in the dog contained in its upper part fine calibered fibers resembling those which formed the visceral efferent fibers of the thoracic nerves, and concluded that these fibers represented the white rami communicantes of the upper cervical nerves. Furthermore he revived, in a new form, the view propounded long before by BELL, in supposing that instead of but two roots, each segmental nerve of the body possessed in addition visceral roots, which, so far as their efferent fibers were concerned, were associated with a lateral column of cells in the central nervous system. Throughout a considerable portion of the spinal region these visceral efferent fibers form the white rami communicantes; in the cranial region they are represented by those fibers which, since the embryological studies of His demonstrated so clearly their distinctness, are generally known as the lateral motor roots. And since the fibers of the lower roots of the spinal accessory belong to the lateral motor series, and according to GASKELL'S view the upper roots represent white rami communicantes, there follows the conclusion that a correlation should obtain between the spinal accessory nerve and the occurrence of white rami passing from the spinal nerves to the sympathetic cord. In the dog GASKELL found in the anterior roots of the spinal nerves from the 10th to the 25th, large numbers of |