NO. 1521. MEASUREMENTS OP CRANIAL FOSS.E—HRDLldKA 



181 



The instruments used were a small, straigcht, rig-id, sharp-pointed 

 compass; the ordinary anthropometric sliding compass; a compass with 

 sharp-pointed, curved branches, each provided at its middle with an 

 additional joint — an instrument that could be easily converted into an 

 endocompass; and a piece of brass wire 16 cm. long and 2 mm. in 

 diameter, l)ent in the middle at right angles. This wire served for 

 measuring the middle fossa, the length being marked on it, and read 

 off with the help of the graduated rod of the sliding- compass. 



To facilitate the presentation of the facts obtained, the measure- 

 ments of the cerebral fosste are not only given in absolute figures, but 

 also in their relation to the greatest external and the mean internal 

 antero-posterior diameters of the skull, and to the sum of the lengths 

 of the three cavities. This latter relation, or index, equals with each 

 fossa the length of the fossa multiplied by 100 and the result divided 

 b}^ the sum of the lengths of the 8 cerebral foss;>? on same side of the 

 skull. 



As to the results of the measurements, it should be constantly borne 

 in mind that they reflect only on the length of the various parts of the 

 brain, and not on other dimensions or mass of these parts, which 

 may be expected to show many additional and perhaps varied fea- 

 tures. These can be determined only by extensive measurements on 

 the brain itself. 



ANTERIOR FOSSiE. 



The figures that follow give averages of the absolute lengths of the 

 anterior cranial fossas in the several series of human adults. These 

 data have only a limited value in crude form, except for showing 

 important differences on the two sides of the skull. In this respect it 

 is seen that the average length of the right frontal cavity is greater in 

 every series without exception. This interesting fact, not brought out 

 before, calls for further detailed observations on the brain in this 

 region. 



Anterior fossx: Average length in adults. 



a Difference from the right fossa. 



