Preservation of specimens. 113 
(6) By turning up the cerebral hemispheres behind, the posterior 
portion of the rounded optic lobes, which lie below, can 
be made out. 
Cut through the spinal cord about half an inch behind the cerebel- 
lum, Take hold of it with forceps and gently lift it up so as to raise 
the posterior portion of the brain from the floor of the skull. Notice 
the nerves which arise from the sides and ventral surface of the medulla 
oblongata. These nerves are eight in number, being the fifth to the 
twelfth craninal nerves. Most of them have numerous roots, The 
chief of them are the hypoglossal, which supplies branches to the tongue, 
the pneumogastic, which supply branches to the stomach, lungs, 
throat, and heart, the auditory nerve, which supplies‘the ear, and the 
trigeminal nerve, which supplies the front of the head. The ‘student 
will not be able to distinguish between these nerves without more ela- 
borate dissection than is here intended, but he should notice the roots 
he is able to make out. 
Now lift the brain completely out of the skull, cutting through the 
nerves with the point of a knife. Examine the lower surface under 
water, and make out :— 
(1) The two large temporal lobes of the cerebral hemispheres, 
which stand out as rounded protuberances on either side, 
about the middle of the length of the brain, 
(2) Immediately between the large temporal lobes is a median 
rounded elevation (infundibulum) to which the small 
rounded pituitary body is attached. The pituitary body 
is usually torn off in extracting the brain. 
(3) In front of the infundibulum may be seen the optic chiasma, 
where the large optic tracts cross each other before passe 
ing into the eyes. Trace back the optic tracis, by 
pushing aside the temporal lobes, to thg large optic 
lobes above. 
The sympathetic nerve system in the palm squirrel is difficult to 
recognise. It consists of a series of delicate nerve-cords and ganglia 
lying on either side of the dorsal aorta, but the students are not likely to 
be able to make them out. 
NOTE ON THE PRESERVATION OF ZOOLOGICAL 
SPECIMENS. 
If the animal is a small one, the simplest plan is to cut one or 
two slits in it, so as to enable the alcohol to penetrate thoroughly, and 
then to drop it into a bottle of spirits of wine. The spirit should be 
changed two or three times, as it gets weak by absorbing moisture out of 
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