Ratios of Body-weights and Brain-weights. Macacus cynomolgus. There are 14 specimens of this species, 7 of males, 6 of females, and I of unknown sex. None of these, to judge by the body-weight, were full-grown animals. The highest brain-weight, 100 grammes, is that of a female weighing only 1203 gms., a case which must for the present be regarded as exceptional. The average weights range between 50 and 67 gms. for the larger animals of the series. TABLE III. Total Averages. Sex. Males 3 64 (1567-2070 gms) | 5697.0 191.0 1899.0 63.7 66 46 62.0 1231.0 62.0 1231.0 62.0 Ratios of Body-weights and Brain-weights. In eight of the ten members of this species the body-weight had been noted (5 males; 3 females.) Two of the males, weighing respectively 8500 and 8610 gms. have brains weighing 128 and 122 gms., giving ratios of 1: 66 and 1: 71. Averages. No. of Range of Body- Body Brain Body Brain Cases Weights. Weights. Weights. Weight Weight. (4590-8610 gms) 33930.0 8967.0 Ratios of Body-weights and Brain-weights. the same number of M. pileatus are all too young to furnish reliable ratios. The average brain-weight of M. sinicus (maximum 75 gms.) is 67.6 gms. Of M. pileatus (maximum 72 gms.) is 63.1 gms. An adult specimen of M. speciosus (3) weighing 5560 gms. has a brain-weight of 98 gms., giving a brain ratio of I:57. The brain of a young specimen (?) weighs 81 gms. A single specimen of M. melanotus has a brain-weight of 80 gms. Judging from these records and allowing for disturbing factors, the following tabulation of the absolute and relative brain-weights, with their variations, may be here proposed. The sexual differences are not discussed at present, for the number of adult specimens is far too small for accurate analysis. As a rule, however, the females seem to have a smaller brainweight, both absolutely and relatively, although the reverse would appear to be true were the total of the tabulated cases to be alone considered. The list of "Probable Averages" in Table V is only tentatively proposed, for the accession of a larger number of adult specimens may materially change certain of the figures. TABLE V. PROBABLE AVERAGES OF BRAIN-WEIGHTS IN THE GENUS MACACUS. A DESCRIPTION OF CHARTS SHOWING THE AREAS OF THE CROSS SECTIONS OF THE HUMAN BY HENRY H. DONALDSON AND DAVID J. DAVIS. (From the Neurological Laboratory of the University of Chicago.) A. CURVES SHOWING THE AREA OF THE CROSS-SECTION OF EACH SEGMENT OF THE MATURE SPINAL CORD. Introduction. The data which are presented in this paper were gathered for the purpose of preparing a curve based on the human spinal cord, with which to compare the areas of white and gray substance found in the cross sections of the spinal cords of other mammals. Reference to the literature shows that with the exception of the curve presented by KRAUSE and AGUERRE (1), which was published while this study was in progress, the series of curves appearing in the text-books and used to show the areas of the gray and white substance at different levels of the cord, was first introduced by Woroschiloff (2), while that investigator was making a study of the conduction paths in the spinal cord of the rabbit. WOROSCHILOFF's curves were based on measurements published by B. Stilling (3). The fact that the records which WOROSCHILOFF chose as the basis for his curves were from a child of five years, and therefore from a cord not completely developed, has been recently pointed out by several writers. That WOROSCHILOFF should have used these particular records of STILLING, instead of taking the records for mature cords, published in the same vol ume, is explained by the fact that only in the case of the fiveyear old child are the areas for the separate funiculi given, and his interest was at that time directed to the funiculus lateralis. Since the white substance in the cord of the five-year old child is, both absolutely and proportionately, less than in the adult, the use of this series of curves to illustrate the gray and white substance in the mature spinal cord is necessarily misleading, yet these curves are at present employed in the text-books, without any accompanying statement to show that they are based on the measurements from an immature cord. areas be those from the adult It is intended in this paper to present a chart which shall more accurately show the true relations between the gray and white matter as they appear in the adult, and thus shall replace the older charts now in use. In order to do this, not only should the measurements of the spinal cord, but there is another correction which applies to all the charts thus far published, including that of KRAUSE and AGUERRE (1), and which consists in representing the segments of the cord in their true lengths. I. Representation of the Length of the Segments. Heretofore, in these charts, the abscissa has always been divided into 31 equal parts-each part representing the length of a segment of the spinal cord. Manifestly this will give an incorrect form to the curve, because the segments of the cord are really of unequal length. As any ordinate representing the area of a cross section applies strictly to the sum of half the distance from it to the ordinates next above and next below the point at which it is erected, it follows that by multiplying the areas represented by any ordinate by the length of the cord to which it applies, we get an approximation of the volume of the segment. It is evident, also, that the volume of a segment thus determined when the divisions of the abscissa are equal, would be different from that determined when the divisions of the abscissa represent the segments in their true length. To make a correct construction, it was therefore necessary to gather data on the |