36 A MANUAL OF ANATOMY. 



bral. These will be found passing to the sinus over the top 

 of the brain. 



The Inferior Longitudinal Sinus. Diag. i. Fig. 8. 



This is a small slit left between the two layers of the dura 

 composing the falx cerebri at its free margin. It extends 

 from the anterior and middle third of the falx to its attach- 

 ment to the tentorium, where it opens into the straight 



sinus. 



DISSECTION. 



Raise the neck with a block, let the head (and with it the brain) drop 

 backward, supporting the brain that it does not draw too forcibly upon its 

 basal attachments. 



Gently insert the fingers of one hand between the brain and the dura, sepa- 

 rating the former from the latter, until the olfactory nerves are seen. Raise 

 these from the groove in the bone with the handle of a knife ; they will 

 usually remain attached to the brain. Let the brain sag backward until the 

 optic nerves come into sight ; divide these close to the bone and the internal 

 carotid artery, which will be seen at the same place. 



The infundibulum is now seen extending to the pituitary gland, located 

 within the sella turcica. To remove the gland cut through the dura covering the 

 cavity containing it, and with the handle of the knife turn the gland out of its bed. 



Still let the brain fall backward and cut through the third, fourth, fifth, and 

 sixth nerves. 



Cut the tentorium along the anterior attachment (to the superior border of 

 the petrous portion of the temporal bone). This will free the brain so that all 

 the remaining nerves can be divided close to the bone. 



The last step is now the most important. Carefully cut through the verte- 

 bral arteries upon either side of the cord, and finally divide the cord across as 

 low as possible. 



The brain is now free, except its attachment by the vein of Galen to the 

 straight sinus ; divide this, after replacing the brain, by separating its hemi- 

 spheres and cutting through the veins just in front of the tentorium. 



Remove the brain and place it in a solution of alcohol (60 per cent.) and 

 chloride of zinc (added to the alcohol until the brain floats midway between 

 the top and bottom of the vessel ; this will insure that when the brain is har- 

 dened it will preserve its normal outlines. With this solution the pia need not 

 be removed until the brain is to be dissected, though it had better be removed 

 in the course of the first week. For complete hardening of the brain in this 

 solution about three weeks is needed). For the dissection of the brain see 

 page 152. 



