A YEAR IN SCIENCE 131 



Directions; Dissect away the skin of a frog's leg. 

 Note the muscles on the leg. What is the general shape 

 of the muscle? Note the tendon attachment of the 

 muscles to the bone. Of Avhat advantage is the tendon 

 attachment? Note that the body of the muscle is sur- 

 rounded by a thin sheet of connective tissue. Find 

 the large muscle on the calf of the leg. Where are its 

 two ends attached? What effect does the contraction 

 of this muscle have upon the lower leg? Upon the 

 foot? The bones of the skeleton serve as places for 

 muscle attachment and as levers for their action. 



CHAPTER XXIV 



NERVOUS SYSTEM 



Exercise 88. Nervous System. (Demonstration.) 

 Object: To study the brain, spinal cord, and nerves. 



Apparatus 



Perch Scalpel 



Dissecting pan Model of human brain 



Scissors 



Directions: Carefully dissect away the roof of the 

 cranium and the dorsal part of the spinal column of 

 the fish to expose the brain and the spinal cord. Note 

 that the brain is divided into a number of regions : the 

 small anterior lobes, the olfactory lobes; the larger 

 cerebral hemispheres; the rounded optic lobes; the 

 single lobed cerebellum; and behind this, tapering grad- 

 ually into the spinal cord, the medulla oblongata. 



