ANATOMY OF NERVOUS SYSTEM 239 



skull. Gently raise brain and spinal cord, divide nerves which 

 spring from them, and lift out whole cerebro-spinal system and 

 place it in alcohol for 24 hrs. 1 Note a) Origin of nerves from 

 both brain and cord, b) Union of brain and cord. 



4) Cut across spinal cord at various levels. Note a) Ar- 

 rangement of gray matter, b) Arrangement of white. 



5) After having hardened spinal cord of lamb or pig in 

 alcohol for 24 hrs., cut thin transverse slices and examine with 

 microscope. 



6) Dissect away skin and muscles covering cranium of calf's 

 or sheep's head. With small saw 2 carefully cut bones in 

 circular direction, so as to loosen top of skull. Carefully re- 

 move top of skull, without injuring the tough protecting mem- 

 brane, the dura mater. 



Demonstrate dura mater enveloping brain. 



7) Cut dura mater away and note processes which it sends 

 between cerebral hemispheres and between them and cerebellum. 



8) Cut processes away and note a) Glistening inner surface, 

 b) Membrane covering brain and full of blood-vessels (pia 

 mater). 



9) Put specimen aside in alcohol or formalin solution for a 

 day or two. When brain has become somewhat hardened, 

 dissect away pia mater on one side and show, a) Cerebral 

 hemispheres and their surface convolutions, b) Cerebellum 

 and its foldings, c) Spinal bulb beneath cerebellum. 



10) With bone forceps cut away remainder of sides and roof 

 of skull. Find a) Nerves to eyes, b) Nerves to nose. 



11) Raise brain in front, cut through vessels, nerves, etc., 

 which attach it to base of skull cavity, and remove it from skull 

 cavity. Note a) Cerebral hemispheres, b) Midbrain. c) 

 Stumps of cranial nerves. 



12) Make sections across brain in different directions and 

 note a) Gray matter spread over most of its surface, b) 

 White matter forming most of its mass, c) Nodules of gray 

 matter imbedded in white, especially in base of brain. 



1 The specimen may preferably be hardened and preserved in a 

 solution made of formalin, 2 parts; alcohol, 20 parts; water, 78 

 parts. 



2 The skull can be cracked with a light hammer and pieces re- 

 moved, without injury to brain. 



