OSTEOMETRY; THE MEASUREMENT OF THE BONES 61 



glass, or some other hard material, the exact cubic contents of which is 

 known. The control skull is measured every little while during the work, 

 perhaps between every two or thiee skulls, and the result compared with 

 the known capacity. A marked discrepancy shows that the work is 

 not being done right, and will indicate whether the medium is too much 

 or too little compressed. 



A natural skull is made into such a control by sawing off the skull-cap 

 in the usual manner, and then treating the entire inner surface with some 

 waterproofing mixture, plugging all the foramina, and finally cementing 

 on the skull cap by the same material. This is then waterproof, and may 

 be accurately measured by this medium, the result of which is definite and 

 invariable. Then when thoroughly dried out it is ready for use. The 

 exact capacity should be clearly marked upon the skull itself. It is to be 

 marked that this result is not necessarily the original capacity of the skull, 

 but that it is probably modified by the waterproofing cement. It is now 

 simply a receptacle of known capacity and with the exact shape of the 

 receptacles with which the anthropometrist is dealing, thus reproducing 

 the exact conditions presented with the normal skulls. 



Finally, as mainly a convenience, in laboratories where there is much 

 of this work going on, a special table should be provided, with a concave 

 top, sloping downward towards the center, where there should be a small 

 hole, communicating with a receptacle placed underneath, through which 

 the extra grains of the medium, the constant spilling of which is inevitable 

 could be collected and returned to the proper place. As a matter of con- 

 venience the top of the table should be large enough to hold the utensils 

 employed, and should be in close connection with a level portion, where 

 the filling of the cylinder and similar work could take place. Each 

 laboratory will easily work out the details of such a piece of furniture for 

 itself. 



While the cranial capacity is an indication of the weight of the brain, 

 the two are by no means the same. Even were the specific gravity of 

 brain substance the same as that of water, there would be a discrepancy, 

 for the cranial cavity contains, not only the brain, but the wrappings, 

 and blood vessels which including the venous sinuses, present together 

 a considerable volume, which if there were nothing else, would make 

 the weight of the brain in grams considerably less than the cranial capacity 

 in cubic centimeters. But, aside from this the specific gravity of brain 

 substance is a little lighter than water, a circumstance which would still 

 further decrease the number in the reduction of cubic centimeters to 

 grams. 



Taking all things into consideration, including the fact that in heads of 

 different size the proportions of brain weight to cranial capacity vary 

 also, Welcker, in 1886, prepared the following table, which is perhaps, the 

 best we have at present (Martin, p. 640). 



