QUESTIONS
23. What do we learn from a comparison of brain weight and intelligence?
24. What is the relation between nervous pathology and mental abnormality?
25. Is phrenology admissible?
26. What view concerning the relation of brain and mind is suggested by the unity of mind?
§ [2]. The Nervous System
[1.] The Elements of the Nervous System
The number of elements making up the nervous system is estimated at about four thousand millions. It will help us to comprehend the significance of this number if we understand that a man’s life devoted to nothing but counting them would be too short to accomplish this task, for a hundred years contain little more than three thousand million seconds. These elements are stringlike bodies, so thin that they are invisible to the naked eye. They are generally called neurons. Within them different parts are to be distinguished. The part which is most important for the neuron’s life is a spherical, bobbin-shaped, pyramidal, or starlike body, called the ganglion cell or cell body, located usually near one of the ends of the long fiber of the neuron, but sometimes nearer the middle of the fiber. The length of the fiber varies from a fraction of an inch to several feet. The fiber may be compared with a telephone wire, inasmuch as its function consists in carrying a peculiar kind of excitatory process.