Questions.
  1. Which lobes of the brain are paired? Give at least two possible causes or reasons for their double structure.
  2. The optic lobes are connected with the eyes. Compare their size with that of the other parts. Of how much use do you think they are to the frog?
  3. If folds or convolutions in the surface of the cerebrum indicate intelligence, thoughtfulness, or mind, what do you infer as to the frog's mental condition and power to think?
  4. Has the frog brain or "brains"? Explain.
  5. Name several things done by an animal's brain.
  6. Which of the spinal nerves are specially large? Why should they be large?
  7. What advantages are there in the frog's having a dorsal nerve cord instead of a ventral one, as the earthworm has?
  8. What would be the effect of cutting or breaking the dorsal root of a spinal nerve? the ventral root? the entire spinal cord? How do you explain the convulsions of the brainless (beheaded) chicken or frog?
  9. What kinds of impulses originate outside of the nerve center, and what kinds in the center?
  10. Sensations reach the cord and brain through the dorsal root of the spinal nerve. What kinds of messages travel through the ventral root, and in what direction do they go?

Suggested drawings.
  1. The brain.
  2. The spinal cord and its nerves.
  3. The nervous system.
  4. A diagram of the cord and its nerves, showing the kinds and the directions of the nerve impulses.
The Endoskeleton of the Frog
Materials.

Prepared frog skeletons mounted in glass-covered boxes or in other cases suitable for individual study; other vertebrate skeletons for reference.

Observations.

The pupil should examine his specimen and identify the following structures:—