THE NERVOUS SYSTEM OF MAN. 43 



thalamus to the corpus and downward to the muscle. 

 This short circuiting becomes more and more perfect 

 until only a little overflow goes to the cerebrum, and 

 thus keeps it aware of what is going on. This view is 

 illustrated by the diagram (Fig. 28), in which .r and m = 

 sensory and motor fibers, ths and csm = sensory and 

 motor cells of thalamus and corpus striatum, and crs and 

 crm = similar cells in the cerebrum. The arrows show 

 the direction of the nerve current. 



Localization of Cerebral Functions. — The cerebrum is 

 the highest ganglion of the brain, and therefore we 

 ought to expect there the greatest degree of differentia- 

 tion and localization of functions. The old phrenology 

 attempted to localize the faculties of the mind; but re- 

 cently there has arisen a new and more scientific though 

 far less ambitious attempt to localize not indeed the 

 faculties of the mind, but the functions of the cerebrum — 

 i. e., the areas of the cerebrum ijeceiving and appreci- 

 ating sense impressions from, and the areas determining 

 and controlling the motions of, various parts of the 

 body. The conclusions arrived at in these investigations 

 are based almost wholly on experiments on the lower 

 animals, especially the monkey, although some of them 

 have been confirmed by observations on man in cases of 

 injury or diseases of the brain. 



These investigations are as yet very imperfect, but 

 some reliable results have been attained. Fig. 29 gives 

 the best established areas. It must be remembered that 

 many of our movements are automatic or semiauto- 

 matic. These are presided over by the lower ganglia, 

 such as the thalamus, the optic lobes, or the medulla. 

 Take the sense of sight, for example. Many of our 

 sight impressions do not rise into distinct conscious- 

 ness, and yet appropriate actions may take place. 

 These are probably determined by the thalamus and 



