THE NERVOUS SYSTEM 225 



6. Describe the differences existing between the gyri and sulci of your 

 specimen and the one described in the text. 



7. Write a description of the ventricles, giving dimensions and boundaries. 



8. Describe the attachment of the pineal body. 



9. Which of the cranial nerves derive their name from their function? 



10. Name the foramina giving passage to one or more of the cranial nerves. 



11. From which of the five parts of the brain do most of the cranial nerves 

 originate? 



12. Describe the choroid plexus. 



13. What is the internal capsule? 



14. Draw a cross-section of the brain made by cutting through the optic 

 commissure and label all parts. 



15. Draw a cross-section of the brain made by cutting through the middle 

 commissure and label all parts. 



16. Draw a cross-section of the brain made by cutting through the corpora 

 qudrigemina and label all parts. 



17. Write a description of the corpus callosum. 



18. Which is the smallest commissure of the brain? 



19. Explain the difference in structure between the white and gray matter. 



20. Describe the cerebellum. 



THE SPINAL CORD 



The spinal cord extends from the foramen magnum through 

 the vertebral canal. It is more or less cylindrical throughout 

 and has a diameter of about one centimeter except in the 

 lumbosacral region, where it grows gradually smaller until it 

 is only one or two millimeters in diameter. In order to study 

 the cord, one should have a mounted transverse microscopic 

 section, and an entire cord in situ with the dorsal wall of the 

 vertebral canal removed, so that the exit of the spinal nerves 

 may be seen. 



The membranes (Fig. no) which envelop the spinal cord 



are the same as those that envelop the brain. The dura mater 



is the external tough coat; the pia mater, the internal delicate 



vascular coat sending a process deep into the anterior fissure 



on the ventral side; and the arachnoid, the very thin membrane 



between the two preceding. The arachnoid lies close against 



the dura mater, but is separated from the pia mater by the 



subarachnoid space, which is filled with a serous fluid called 



the cerebrospinal fluid. It is apparently the same as that in 

 15 



