658 PHYSIOLOGY OF THE CEREBRUM 



Artificial stimulation of the cortex back of the angular gyrus in the 

 monkey (H. Munk, Schafer) gives conjugate movements of the eyes toward 

 the opposite side, the plane of vision being at the same time directed upward, 

 downward or horizontally, according as different points of this region are 

 stimulated. The latent period of these movements is longer than that of 

 corresponding eye movements which appear on stimulation of the frontal lobe, 

 they are also obtained after removal of the frontal lobe; hence are probably 

 evoked through the above-mentioned subcortical centers. The same move- 

 ments occur when the occipital cortex and the eye region of the opposite 

 frontal lobe are stimulated simultaneously. 



Movements of the iris also can be aroused by stimulation of the cerebral 

 cortex. Dilatation of the pupil is most easily obtained in the monkey by stimu- 

 lation of the motor region for the eye muscles and of the occipital lobe. This 

 dilatation appears when the cervical sympathetics are cut, and probably must be 

 regarded as at least partly due to an inhibition of the sphincter muscle. Con- 

 striction of the pupil seems to be obtained only as an exceptional result of corti- 

 cal stimulation. 



E. RECAPITULATION 



From the facts which have just been brought forward with regard to the 

 cortical areas of the nerves of special sense, it appears probable that they, 

 like the motor areas, become more sharply concentrated the higher we ascend 

 in the scale of mammals:, also that their importance for special sensations 

 becomes greater and greater. Moreover, it is evident that, as a general rule, 

 efferent paths from all the sensory cortical areas are so arranged as to convey 

 impulses to just those muscles which are of the most service to the particular 

 senses. Thus, the cortical field for the sensory nerves of the skin, of the 

 muscles and the joints lies in the immediate vicinity of the great motor cor- 

 tical area or practically coincides with it ; we get movements of the ears from 

 the temporal lobes where lie the auditory areas, and movements of the eyes 

 from the occipital region. We shall discuss the deeper physiological and 

 psychological significance of these cortical areas in the following section. 



SECOND SECTION 



THE PSYCHO-PHYSICAL FUNCTIONS OF THE 

 CEREBRUM 



While an exhaustive discussion of the psychical activities of man is plainly 

 out of the question in this book, a brief summary of the most important facts 

 of modern physiological psychology seems called for here, because, quite inde- 

 pendently of any particular psychological system, or of any spiritualistic or 

 materialistic point of view, these facts may of themselves afford us valuable 

 insight into the complex mechanism of cerebral activity. We designate these 

 functions psycho- physical in order to expressly indicate that we shall discuss 

 them not from the standpoint of metaphysics, but solely from the standpoint 

 of physiology, and without wishing to take any position with reference to 

 spiritualism or materialism. 



