236 STUDY OF BRAINS OP SIX EMINENT SCIENTISTS AND SCHOLARS. 



First, and most important, those of the cerebrum comprise its principal diameters 



and circumferences, the arc measurements along the dorsi-mesal border and a series 



of horizontal distances to be described below. 



The principal measurements of the cerebrum are given directly in centimeters ; 



they are as follows : 



Maximum length, left hemicerebrum. 



Maximum length, right hemicerebrum. 



Maximum width of cerebrum. 



„ , , ^ , f Breadth X 100 



Cerebral index \ =f -; 



I Length 



Horizontal circumference : 



Maximum width, left hemicerebrum. 



Maximum width, right hemicerebrum. 



Left occipito-temporal length. 



Right occipito-temporal length. 



Length of callosum. 



Left centro-temporal height. 



Right centro-temporal height. 



Left centi'o-olfactory height. 



Right centro-olfactory height. 

 The arc measurements are made according to Cunningham's method, consisting 

 essentially in the measurement by means of a tape (I employed one 6 mm. wide) along 

 the dorsi-mesal margin from a point corresponding to the level of the lateral part of 

 the orbitofrontal border, to the most caudal point on the occipital pole. From the 

 cephalic point measurements to the dorsal end of the central fissure (or its transit 

 across the dorsi-mesal border) and thence to the dorsal intersection of the occipital fis- 

 sure are recorded and converted into centesimals of the total fronto-occipital marginal 

 arc. The component segments of the total arc represent relative values to which the 

 terms frontal index, parietal index and occipital index are given and they afford the best 

 means possible for determining the relative marginal extent of these cerebral lobes. 

 Thus the importance of measuring the occipital index was recognized by even so early 

 an observer as Gratiolet, and later observations would seem to suggest that, other 

 things being equal, relative smallness of the occipital arc signified superiority of cere- 

 bral development. Cunningham has ascertained the occipital index in several of the 

 primates : 



