110 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



barely sufiQcient pressure, except ou the palate, to make it stick ; if too miicli pressure is applied 

 it will force iuto the crauial cavity the material ia the foramiua at the base of the skull, which has 

 previously beeu applied with such great care. Next roll out on the breadboard, with the rolling- 

 pin, a sheet of the putty of a size sufiBcieut to cover the vertex of the skull. It should be of uniform 

 thickness — not less than an inch throughout. Now the skull is laid on the table, base downwards 

 — and this position is important — the cap of putty is placed on the vertex, pressed closely on and 

 worked around until it completely covers the cranium, leaving only the superior alveolne, parts, 

 perhaps, of the zygomatic arches, and the margin of the foramen magnum exposed to view. The 

 completed, the skull is ready to be filled. 



6. In the mean time, or before you begin operations, you have the half-gallon measure filled to 

 within about 3 centimeters of the top. Tbe skull is now held in the hands of an assistant, base 

 upwards, in such a manner that the plane of the foramen magnum .shall dip forward at an angle 

 of 45 degrees or more with the horizon. This is necessary in order that, as tbe water rises in the 

 skull, air may not be imprisoned in the middle cerebral fossae. I have seen an error of 10 centim- 

 eters result from a neglect of this precaution. Now take in the left hand the tin vessel of water 

 and have the stop-cock either in, or convenient to, the right hand. Empty the water from the 

 vessel iuto the skull through the foramen magnum as rapidly as you can, without sjnlling, until 

 the skull is nearly full. Then rai)idly lay down the tin measure, open your stop cock and com- 

 plete the tilling of the skull, taking good care that you fill it at once rapidly and exactly. Much 

 depends on the care with which the last few drops are added. As the assistant sees the water 

 rising to the edge of the foramen magnum, he will gradually elevate the anterior portion of the 

 skull until the plane of the occipital foramen is horizontal, and when the stop-cock is opened he 

 will bring the skull close to the edge of the pan so that the process of emptying may begin the 

 instant the filling is done. 



7. The moment you consider the cranium properly filled, close the stop cock and notify your 

 assistant, who should instantly begin to pour out the water; this is best done by holding the skull 

 in such a manner, occiput depressed, that during a greater i)art of the time the air may enter 

 freely as the water runs out. I might convey an idea of the approved method by saying that the 

 occipital region is held fixed and the superior alveolar region made gradually to describe an arc of 

 180 degrees, until at the end of tbe operation tbe base of the skull is downward. Once more the 

 anterior portion is elevated so as to allow any accumulation in the anterior and middle fossie at 

 the base to come back to the foramen magnum, and again depressed and rocked a little to each 

 side to empty tbe posterior fossne. This completes the task of emptying. Not a drop of the 

 subsequent drainage from the skull, no matter how abundant it may be, sbimld be taken into 

 account. The filling and emptying of the skull should be done as rapidly as is consistent with 

 l)roper care. Upon this celerity depends as much as on anything else the correctness of tbe 

 results. A person who has gained a little experience can till a skull of 1,400 cubic centimeters 

 accurately in 45 seconds and empty it in 15 seconds; both operations together should not occupy 

 more than one minute. We have filled in 30 and emptied in 12 seconds, but for emptying we 

 would recommend that just 15 seconds be always consumed. 



8. Next comes tbe cubature: First wipe out the measuring-glass carefully, in case it is moist 

 from a previous measuring, and then em]>ty the water from the pan carefully into the glass; every drop 

 that can drain out being allowed to fall. Tbe measure is then placed on a carefully leveled table. 

 A small quantity of lycopodium is put in the insufflator and blown on the surface of tbe water. 

 This makes the true general surface of the water easily discernible and prevents us from mistaking 

 for it the edge of the water which has been raised by capillary attraction on the surface of the 

 glass. Then read oft' the number indicated and add one centimeter for the dry shellac in the skull. 



9. Now take all the putty carefully from tbe skull, have tbe latter well cleaned and put it 

 away in a dry, warm apartment for a week or more until it is as dry as it was before the measure- 

 ment was begun ; this is determined by again weighing it, then you measure it once more to 

 verify your former experiment. 



Some further comments on the appliances and proceedings must now be given, which could 

 not be introduced before without sacrifice of clearness. 



The varnish has beeu only recently employed. The propriety of using it was early thought 



