GROWTH OF THE CORPUS CALLOSUM 39" 



square millimeter, using the Amsler planimeter. The values 

 obtained were averaged, reduced to the actual values for the 

 area of the corpus callosum on the slide, and recorded. As I 

 measured all the sections in the same manner, the data thus 

 obtained are comparable among themselves. These data are 

 presented in table 1 in a condensed form, but the individual 

 records have been filed in the Archives of The Wistar Institute. 



GROWTH IN AREA OF THE CALLOSUM IN SAGITTAL SECTION 



a. Growth in callosal area on body weight 



Table 2 is based on table 1 and contains the records for the 

 area of the brain as well as the callosum. 



According to Donaldson ('08), the brain weight goes with the 

 body weight in so nearly a like manner in both sexes that we 

 have felt justified in combining our observations on males and 

 females both in the tables and for discussion. 



Chart 1 shows how the observations given in table 2 are- 

 distributed when entered in relation to increasing body weight, 

 which in turn implies increasing brain weight. As can be seen 

 by inspection (column D, table 2), the 'scatter' of the entries is 

 not very great. It is of interest to find that the mean observed 

 values (dotted line in chart 1, A) follow closely the theoretical 

 logarithmic curve. The theoretical curve, about which the 

 observations cluster, is represented by the continuous line in 

 chart 1, A, and was computed by means of the formula: 



ij = 0.184 + 0.0003 X + 2.08 log .t. .. .Formula (1) 



in which y is the area of the callosum in the sagittal section, 

 in millimeters, and x the weight of the body, in grams. This 

 formula is based on the general formula y = a + bx + c log x, 

 already published by Hatai ('11). The values of x and y are 

 given in column A and E of table 2. The theoretical curve 

 based on this formula gives a very good graduation of the area 

 of the callosum for any value of x. An examination of chart 

 1, A, shows that the growth curve of the callosal area can be 

 divided into two parts: 1) the period of earlier and more rapid 



