112 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



this had to be remedied, as must be done in all cases. Of course it is essential that the axis of the 

 glass cylinder should be perfectly perpendicular ; so not only should the bottom of the stand be 

 made quite even, but the stand on which the glass is placed to be read should be carefully leveled. 



Different substances have been tried to define the surface of the water. Any dry impalpable 

 powder of low specific gravity may do ; many such powders would, no doubt, answer as well as 

 lycopodiuiii. Lampblack gives a beautiful and accurate line of demarkation, but it does not work 

 well in the insufflator and is a dirty thing to handle. Charcoal tends to sink. A mixture of two 

 parts of lycopodium and one of charcoal floats well and gives a more distinct line than lycopodiuiu 

 alone. 



As it is stated that the measuring-glass of Ranke is graduated with water at 14 degrees cen- 

 tigrade, we have adopted this as the temperature of the water we use. But it is important that not 

 only should the water, when taken from the reservoir, be of this temperature, but that the skull 

 and all the vessels used should be of the same temperature. Indeed, it is well if the general tem- 

 perature of the ai>artment in which the measurements are taken does not vary much from this 

 standard. If water is taken from a vessel at 14 degrees, poured into a colder skull, thence through 

 a colder atmosphere into a colder pan, and thence into a colder glass, it will not be at the standard 

 temperature when you come to read, and will register too low. The reverse will be the case if the 

 temperature of the vessels and surrounding atmosphere are higher than 14 degrees. If the tem- 

 perature of the room has been maintained for some hours at 14 degrees, tbere is little doubt that 

 the skull and all the vessels will be at the right temperature ; but if the heat has been increased 

 or diminished but a short time before you begin work, water of the proi)er temperature must be 

 put m the vessel before the measuring begius ; but of course the skull cannot be thus regulated. 



It will be seen in Tables I and II that the second measurement was taken in many cases within 

 a week of the first, as it was found that in this time the skulls were reduced by evaporation to 

 their former weight. It seems they had ample time to contract, for we record only one case (21, 

 Table I) where the second measurement was greater than the first. Nevertheless, siuce Broca 

 maintains* that the contraction of a drying skull is not always in direct ratio to the loss of weight, 

 it would perhaps be well to allow a longer time for drying than we have done, in an apartment 

 maintained at a low temperature. Care must be taken, however, that the weight, aiul therefore 

 the capacity, are not reiluced below the original standard. 



The cutu-e work of applying the putty and measuring the skull need not ()ccu[)y more than 15 

 minutes. The time necessary for gauging and cubature of the skull after the putty is applied 

 need not exceed 3 minutes. The task of cleaning the skull may be deferred for some hours 

 and left to an unskilled assistant. Two persons have with us been employed ia doing the work 

 of filling, one to pour in the water while the other held tiie skull, but I think means might be 

 devised by which, if necessary, one person could do the work. 



We will now consider the merits, diflftculties, and disadvantages of this method and see how 

 it compares with others. 



Dr. Topinard says, in the passage quoted above, that one of the prime difficulties is that the 

 water gets into the sinuses and vacuoles of the skull and returns when the skull is drained (6goutt6) ; 

 this is true, and if the skulls were drained in our system we would never arrive at comparable or 

 uniform results. As for the larger foramina, we fill them with putty. The sutures, the sinuses, 

 and the osseous tissue take up much water, some of which they part with in a few seconds or 

 minutes, some of which remains for hours and days, and is finally only carried away by evapora- 

 tion. Now, that which soaks into the bony substance remains there until lost by evaporation ; 

 that which reaches the closed sinuses, which I believe to be very little during the few seconds the 

 skull is tilling, does not get time to return in emptying, and that which enters the sutures is held 

 there some time by capillary attraction and departs slowly. Again, it is the sutures and sinuses 

 at the base of the skulls which are the most extensive and the most bibulous, and these, at the 

 close of the operation for emptying, are held in such a position that they cannot part with their 

 water before the cranial cavity is emptied. Observations taken on sawed skulls and on skulls 

 having the external tables of the frontal and sphenoidal sinuses broken, seem to- corroborate these 



•Etudes sur les propridtds hygroiu^triquea des craues, cousid^r^es dans leurs rapports avec la cranometrie, Revue 

 d'Anthropologie, Paris, 1874, iii, pp. 385 to 444. 



