THE NERVOUS SYSTEM OF MAN. ,, 



There are, however, many kinds of aphasia. The 

 one above mentioned is motor aphasia. But there is also 

 an auditory aphasia (a.aph), in which the patient can 

 speak but can not understand spoken words; a visual 

 aphasia (v.aph), in which the patient can not read ; and, 

 finally, a graphic aphasia [g.aph), in which the p'atient 

 can not write. These are situated in different parts of 

 the brain and shown on Fig. 29.* 



The higher operations of the mind, such as self- 

 consciousness, thought, moral sentiment, etc., which 

 the older phrenology sought to locate, are possibly not 

 localized at all, but involve the co-operative activity of 

 the whole brain, and such co-operative activity is prob- 

 ably controlled by special centers of association yet un- 

 known. \ 



Dextraliiy. — We have said that aphasia is an affec- 

 tion of a certain convolution of the frontal lobe, espe- 

 cially on the left side. This naturally leads one to draw 

 attention to the fact that the cerebral hemispheres 

 control each the opposite side of the body. The fibers 

 from the gray matter of the cortex coming down cross 

 over to the other side. It would seem, therefore, that 

 the greater dexterity of the right side — right-sidedness 

 — is the result of the higher development of the left 

 cerebral hemisphere — left-brainedness. Dexterity is a 

 more perfect co-ordination of muscular motion. Now, 

 there is nothing in which this is more conspicuous than 

 in speech. 



SECTION II. 

 Spinal Cord. 



We have already said that the basal part of the brain 

 may be regarded as an intercranial continuation of the 



* Duval, Rev. Sci., vol. xl, p. 769, 1887. 



•f Turner, Brit. Assoc. Address, Nature, vol. lvi, p. 525, 1897. 



