REMOVAL OF THE PIA. 429 



pains are needed in connection with the hypophysis and the nerves, 

 and all pulling must be avoided. On one side, at least, it is well to 

 leave the dura still attached to the nerves and the great Gasserian 

 ganglion upon the N. trigeminus (Fig. 115 ; Plate II, Fig. 3, Gn. G.), 

 to be more completely removed at the time of the removal of the pia. 



§ 1105. Transfer to the Alcohol. — Place a large spoon or watch 

 glass at the side of the brain, and puU the cotton which supports it, 

 so as to roll it into the glass, resting upon its dorsum. Let the 

 Ibrain slide from the glass into the alcohol so as to rest upon the 

 <5otton therein, still with the ventral side up. 



Set the bowl with the alcohol in a cool place, and change the 

 position of the brain at intervals of 5-10 hours during the first three 

 days, by pulling the cotton in various directions. At the end of 

 about three days, transfer the brain to 95 per cent, alcohol, where it 

 may remain indefinitely. For a few days, however, it should rest 

 upon cotton, and its position be occasionally changed. For the 

 management of alcohol employed in the preservation of brains, see 

 §§ 286, 296. 



§ 1106. Weighing the Brain.— If this is to be done, handling of 

 the brain may be avoided as foUows : Place the bowl of alcohol 

 into which the brain is to be put upon the scales, and pour in alco- 

 hol of the same strength until it balances an even number of grams, 

 e. g., 400, 410 or 420. While the brain is in the spoon or watch 

 ^lass, pour over it some of the same alcohol, and then let the latter 

 drain off as much as possible by tilting the glass and supporting 

 the brain with the fingers or a bit of cotton. Then transfer to the 

 bowl of alcohol as above directed, and the increase in weight will 

 represent, with approximate accuracy, the weight of the brain. 



§ 1107. Removal of the Pia. — This is most easily accomplished 

 at the time of the removal of the brain to the stronger alcohol. At 

 any subsequent period the pia is apt to be more firmly adherent. 

 If the brain has been allowed to dry at all during its removal from 

 the skull, the pia comes off with great difficulty, or parts of the 

 cortex are torn off with it. 



§ 1108. Instruments and Materials. — Coarse and fine forceps ; 

 medium or fine scissors ; wetting bottle of 15 per cent, glycerin ; 

 cotton thoroughly wet with water, and so molded as to form a sort 

 •of shallow cup in which the brain may be grasped, or on which it 

 may rest without danger of rolling off. 



Place the brain upon the cotton, and wet it with the glycerin. 



