90 LABORATORY EXERCISES. 



4. Test the various portions of the tongue with 



vinegar. 



5. Record your results as follows: 



47. STUDY OF BRAIN OF SHEEP. 



Materials : Sheep heads can be obtained from any butcher, and 

 the brain may be carefully removed in the following way: With a 

 small saw make two cuts along the top of the skull, each about 

 three-quarters of an inch from the mid-line of the head, care being 

 taken not to cut into the brain. The saw-cuts should extend from 

 front of the eye-sockets back to the openings into the ears. Con- 

 nect these longitudinal cuts by sawing across the skull in the regions 

 just indicated. In this way a rectangular piece of bone is loosened 

 which can be pried off by the use of a chisel. The cerebral hemi- 

 spheres of the brain, enveloped in tough dura mater, are thus ex- 

 posed. The bony top of the skull should be preserved in 4% solu- 

 tion of formalin (one volume formalin to ten volumes of water). 



Continue the side cuts backward through the hard bony pro- 

 cesses by which the skull was attached to the spinal column, and 

 with a chisel pry off the rest of the top and back wall of the cranium. 

 Beneath it lie the cerebellum, the medulla, and the beginning of the 

 spinal cord. 



To remove the brain from the skull the head should be supported 

 with the tip of the skull downward. By means of forceps take hold 

 of the dura mater on the ventral surface of the spinal cord and care- 

 fully pull it away from the base of the cranium. With dissecting 

 scissors or with the point of a scalpel cut off the various nerves, 

 leaving as much as possible of each nerve attached to the brain. If 

 the opening in the roof of the skull is not large enough to allow the 

 brain to be taken out easily, the sides can be cut away with bone 

 forceps. 



