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A YEAR IN SCIENCE 



divided into three regions: fore brain, mid brain, and 

 hind brain. The latter is continuous with the spinal 

 cord. 



The fore brain is called the cerebrum. It is enor- 

 mously developed, forming about three-fourths of the 



Spinal Cord . 



Fig. 178. Side view of the brain. 



entire brain, and is divided by a deep fissure into a 

 left and right hemisphere. Many folds and ridges, 

 called convolutions, greatly increase its surface. 



The mid brain is an isthmus connecting the fore and 

 hind brains. 



The hind brain consists of the cerebellum, the pens 

 varolii, and the medulla oblongata. The cerebellum has 

 a wrinkled surface, but is somewhat different in appear- 

 ance from the folded cerebrum. It is the largest part, 

 of the hind brain and is partly covered at the back 

 by the cerebrum. 



The medulla oblongata lies in the cranium, but it is 



