68 A MANUAL OF ZOOLOGY 



in size? Notice several pairs of nerves coming off from 

 the spinal cord. How many are jthere? What makes up 

 each pair of spinal nerves.? The spinal nerves may be seen 

 better by cleaning the ventral cavity. ■ They will appear as 

 white cords extending to , different parts of the body. 

 Work them out carefully and note that there are ten of 

 them. Work out the spinal column and locate the spinal 

 ganglia. Upon which root do you find them? Locate the 

 sympathetic nervous system. Is there any connection with 

 the spinal nerves? Note, locate, and name the -ten .pairs of 

 cranial nerves. Study prepared slides of nerve tissue, 

 spinal cord, and isolated nerve cells for the microscopic 

 structure of the nervous system. Distinguish between 

 medullated and nonmedullated nerve fibers. Note the axis 

 cylinder, nodes, and internodes. Pick out several cells 

 'in the slide and compare them in shape. In the spinal 

 cord note the position of the gray, and the white matter.. 

 What constitutes each? Study a section of the spinal gang- 

 lion. Of what does it consist? What membranes cover 

 the central nervous system ? Make a drawing of the dorsal 

 and one of the ventral, surfaces of the brain. 



THE EYE — Note the following structures before mak- 

 ing any dissections. The shape, the sclerotic coat, the 

 cornea, the iris, the pupil, the optic nerve. With a sharp 

 knife divide the eye ball into an anterior and posterior 

 half. Note the lens in the anterior portion. Locate the 

 anterior chamber. What does it contain? The vitreous 

 humor fills the posterior chamber. Describe the vitreous 

 humor. Locate the choroid coat as a lining for the scler- 

 otic coat. What is its color?. Note a transparent mem- 

 brane lining the eye ball, the retina. At what point Is it 

 attached to the eye ball? Dissect an eye of a sheep or of 

 an ox and compare in every respect with that of the frog 

 as above. Make a diagram of the antero-posterior section 

 of the eye and name all of the parts. Study prepared 

 slides of the anterior and the posterior quarters of the eye. 

 Work out the meaning of all the parts shown, especially 

 the ciliary muscles, the iris, the cornea, the coats of the 

 eye, the optic nerve. Note carefully their structure. 



THE EAR— Study a series of sections of the~frog's 

 head through the ears, made by decalcifying, embedding 



