XVI. 

 THE NERVOUS SYSTEM. 



The Brain. 



The nervous tissues of the body may be divided into 

 several parts ; the brain, the spinal cord, the nerves, the 

 ganglia, and the sympathetic nerves and ganglia. 



A. The Brain of a Sheep. 



Materials. The head of a sheep. Cotton batting. Potassium 

 bichromate. Formalin or formaldehyde. A human brain if pos- 

 sible. 



Apparatus. A meat-saw. Bone forceps. Glass jar. 



The head of a sheep, a rabbit, or of some other verte- 

 brate may be obtained and the brain be taken from it. In 

 order to obtain the brain in good condition the roof of the 

 skull must be removed. With a meat-saw, cut across the 

 front of the skull just back of the eyes, and then saw, 

 backward along either side of the head, just above the 

 ears to the opening in the skull where the spinal cord 

 joins the brain. Carefully remove the large, nearly tri- 

 angular piece of bone. With the handle of a scalpel, 

 slowly free the brain with its coverings from the skull. 

 Take care not to cut the roots of the cranial nerves close 

 to the brain, but preserve them as long as possible. Wrap 

 the brain in a piece of cotton batting to prevent its weight 



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