1868.] 443 [Wyman. 



cumstances, adjust themselves to the least space with difFerent deorees 

 of facility. Shot and peas having a spherical shape the position in 

 which they happen to fall is a matter of indifference, since all their 

 diameters are equal. The other bodies whose diameters are unequal, 

 require moi-e or less of shaking and pressure in order that they may 

 be packed in the smallest compass and thus an exaggeration of the 

 capacity avoided. With proper care, correct measurements can of 

 course be made with either of the materials mentioned in the table, 

 and in practice no one would omit to shake down and compress the 

 material in the measure to the same degree that he would in the skull. 

 The object of the table is only to show the comparative amount of 

 compression and adjustment required. To present the subject in 

 another way, if a litre is filled with peas, and then shaken, it will 

 diminish one per cent, in bulk, while, under similar cut urn stances, 

 coarse sand diminishes fifteen per cent. In the first case the error 

 will not exceed one per cent. ; in the second it may be, unless great 

 care is taken, much more. Of the different substances used, peas 

 and shot, on accoimt of their spherical shape, gave the best results, 

 and coarse and fine sand the worst, on account of the irregular shape 

 of the grains, the small size of these, for the finer the mnterial the 

 greater the error, and the roughness of their surfaces. As to peas 

 and shot, the last give the most accurate and uniform results, while 

 the latter, being less perfect spheres, lead to a slight error, but have 

 the advantage in lightness, thus making manipulation more easy. 

 Sand has the further disadvantage of filling many angles, canals, and 

 foramina not occupied by brain, and therefore of exaggerating the quan- 

 tity of thi's last, and in requiring that the ibramina in the orbit should 

 be plugged to prevent its escape. This last objection is of little 

 moment when a single skull is to be measured, but is considerable when 

 the number is large. By using bodies of the size of peas or shot, the 

 inconvenience and the exaggeration are both avoided. The diffei-- 

 ence in the table between the amount obtained by measuring with peas 

 and shot de]iends upon the larger size of the latter. 



There is still another step to be taken, even if an exact measure- 

 ment of the cranium has been made. The brain, as already stated, 

 does not fill the cranial cavity; a space, variously estimated, is occu- 

 pied by the membranes and the vessels, which should be deducted 

 from the general internal capacity. Welcker estimates this at from 

 11.6 to 14 per cent, of the whole cavity, according as the skull varies 

 in size. Dr. J. Barnai'd Davis makes a correction of 10 per cent. 



Brain, not cranial measurement, is, of course, the object of the 

 study of the capacity of the skull; but until some definite results are 

 obtained, which will enable the observer to make accurate corrections, 



