112 Elementary Manual of Zoology. 
Force open the mouth and examine the pair of large chisel-shaped 
teeth (incisors) both in the upper and lower jaw. These teeth continue 
to grow throughout life, and are characteristic of the order ( Rodentia) 
to which the palm squirrel belongs. 
Cut away the soft skin of the roof of the mouth, and make out 
where the cavity of the nostrils passes out behind just opposite to where 
the trachea begins, so that the air is able to pass in breathing directly 
into the lungs without entering the mouth, Eustachian tubes connect 
the cavities of the ears with the posterior nasal chamber, but the 
students will probably be unable to make them out. 
Turn the specimen over and pin it out into the weighted bark with 
the back uppermost. Take off the skin, and dissect away the 
muscles from the back of the neck. Insert the point of the scissors into 
the large opening (foramen magnum) of the skull behind, and carefully 
dissect off the back and sides of the skull, taking care not to injure the 
soft brain that it contains. Continue the dissection down the back, 
cutting through the spinal arches so as to expose the spinal cord. 
Hardening the brain by placing the specimen in strong aleohol for a few 
days after the roof of the skull has been removed facilitates subsequent 
dissection, but the more important features can be made out in the 
fresh state. 
Notice that the skull is lined with tough membrane (dura mater), 
which will probably Le torn offin removing the bone. Beneath this is 
a much thinner membrane (pia mater), which closely invests the brain 
and contains the superficial blood-vessels. Pick the brain as clean as 
possible with forceps and make out the following parts, begioning from. 
behind :— 
(1) The medulla oblongata, which is the expanded end of the 
spinal cord where it passes into the skull. 
(2) The cerebellum, which is a much foliated mass lying above 
the medulla oblongata. 
(3) The cerebral hemispheres which are two smooth elongated 
masses in front of the cerebellum, They take up the 
greater part of the upper portion of the cavity of the 
skull, ; 
(4) Lying in the angle between the cerebral hemispheres and 
the cerebetlum is the small pineal body, which is very 
liable to get torn away in removing the roof of the skull. 
It represents the rudiment of what was once a median 
eye. 
(5) The olfactory lobes, which are two small rounded masses lying 
in front of the cerebral hemispheres. They give origin 
to the olfactory nerves. 
