Method XIX 107 



nerves. Since it is very desirable to remove the brain with all the 

 cranial nerves attached, it will be safer not to try to remove this 

 ventral portion of the dura. 



Make the necessary incisions in the scalp and pull it aside 

 far enough to be out of the way of the saw. Let the line of the 

 saw pass through about the middle of the frontal bone, and 

 around and downward on each side through the inferior portions 

 of the parietal bones near the temporo- parietal suture. Then turn 

 the lines farther downward so as to pass through the occipital 

 bone in line with the occipital condyles, thus forming a wide V with 

 its point opening into the foramen magnum. 



Use the saw carefully lest it pass through to the brain. It is 

 best not to saw through the bones entirely ; when almost sawed 

 through they may be more safely wrenched apart with a chisel. 



When the bones are separated along the entire length of the 

 saw, the cap thus detached may be pulled off, leaving the dura 

 mater covering the brain intact. Now, with blunt-pointed 

 scissors, the dura mater may be cut around just below the line 

 of the saw, and the brain is ready to be removed. 



The brain may be removed with less danger of pulling off 

 the cranial nerves if the removal is begun from behind at the 

 medulla oblongata. First, however, gently press back the frontal 

 lobes and carefully detach the olfactory bulbs from the cribriform 

 plates. Then, with the hand, lift the medulla carefully, and as 

 the cranial nerves come into view, clip them off close to their 

 entrances into their respective foramena. 



2. To fix and harden, place the freshly removed brain (and 

 spinal cord if kept attached) in 3 or 4 times its volume of 10 

 per cent, formalin. 



The bottom of the vessel in which the brain is placed should 

 be padded with absorbent cotton to prevent the fresh specimen 

 from becoming flattened by contact with the bottom, and thus 

 hardening in that shape. For the same reason it will be well to 

 turn the specimen three or four times dtiring the first 24 hours. 



Change the fluid ^after 24 to 48 hours. If the specimen 

 is small, a 5 per cent, solution may be used in the change. 



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