THE BRAIN 303 



removed by cutting away the skull. After opening the top of the skull, 

 place it with the brain in Muller's fluid or formalin for a few days, when 

 the brain will be hard and can be removed with little injury. 



127. In the frog, note the medulla, then the thin cerebellum, look- 

 ing like a disk of paper with its edge inserted just above the medulla. 

 Note the swelling optic tubercles, and then the long, pointed halves of 

 the cerebrum. 



Next compare the same parts on a bird's brain. Note the similar 

 medulla and optic tubercles. Note the large cerebellum forming a half 

 moon above the optic tubercles, and marked with cross fissures upon 

 its back part. Note the cerebrum in front, shaped like a chestnut and 

 as large as the rest of the brain. 



Next compare the same parts in a mammal's brain. Note the similar 

 medulla, but the larger cerebellum. The optic tubercles are obscured 

 by the cerebrum. Note the cerebrum, large enough to cover almost 

 all the rest of the brain. Note the convolutions. 



Now compare these brains with a model or a picture of the brain 

 of man. Note the large frontal regions in man and the larger and 

 more numerous fissures and convolutions, and that the cerebrum com- 

 pletely covers all the other parts of the brain. 



128. When the skull of an animal is opened, note the lining of tough 

 and thick dura mater, which may be peeled off with little difficulty. 

 Note that it extends in between the two hemispheres of the brain and 

 between the cerebrum and cerebellum. Underneath it, note the deli- 

 cate meshes of the pia mater, containing numerous blood tubes. Note 

 that it dips into all the fissures and contains a small amount of a thin, 

 clear fluid. 



129. Examine a specimen of the gray matter of the cerebrum or 

 cerebellum with a microscope magnifying 400 diameters. Note its nerve 

 cells with fine branches. The white matter will appear like a collection 

 of ordinary nerve fibers. Sketch the specimen. 



REVIEW TOPICS 



1. Name the different parts of a frog's brain in order, 



and tell how they differ from the same parts in a 

 man's brain. 



2. Describe the two coverings of the brain. 



