CEREBRAL LOCALIZATION 687 



atrophic changes in the region of the cuneus, which is situated above 

 this fissure. 



In addition, Flechsig 1 has proved by means of the myelinization 

 method that the optic fibers terminate largely in the region situated 

 along the calcarine fissure, i.e., in the cuneus as well as in the gyrus 

 lingualis. The same inference may be drawn from the clinical data 

 compiled by Crispolti (1902), which show that the most permanent 

 types of hemianopia result from lesions of this particular area. 



The tendency, therefore, is to regard the cuneus as a more impor- 

 tant area of the visual center than the lobulus lingualis and fusiformis. 

 Besides these regions, however, which border upon the calcarine fissure, 

 the psycho-visual sphere also embraces the three occipital convolutions 

 and even encroaches upon the outlying districts of the parietal and 

 temporal lobes. Evidently, the fields named last are set aside for 

 visual memory. Any attempt, however, to localize these psychic 

 areas more sharply must meet with failure. Thus, it does not seem 

 correct to assume with Henschen and in accordance with the theory 

 of Munk, that the retinal elements are projected in the visual center 

 as individual units, because we are in no position to-day to support a 

 contention of this kind by facts. This projection would imply that 

 those elements which are situated in the upper area of the retina, are 

 associated by the cellular units of the cuneus, .while those situated 

 below are associated by the lobulus lingualis. The point most 

 frequently mentioned against such an almost mathematical subdivi- 

 sion of the visual center into visual units of definite value, is the fact 

 that Monakow 2 and Bernheimer 3 have shown that the fibers innervat- 

 ing the yellow spot, are widely scattered through the occipital cortex, 

 and do not terminate in a circumscribed area of this region. 



The Connection between the Visual Center and Others. The 

 fact that the stimulation of the occipital cortex gives rise to muscular 

 movements, points toward the existence of definite anatomical con- 

 nections between the visual center and the musculomotor mechanism. 

 The stimulation of the upper surface of the right lobe causes the eyes 

 to be turned downward and toward the left, while the excitation 

 of its posterior region produces a deviation of the eyes upward and to 

 the left. Furthermore, a purely lateral movement to the left may be 

 evoked by stimulation of the mesial surface. It must be conceded, 

 therefore, that the visual sensations are expressed in this case in 

 accurate muscular movements, and that this end can only be attained 

 by efferent impulses which traverse the occipitothalamic radiation 

 and eventually find their way into the nuclei and distal ramifications 

 of the third, fourth and sixth cranial nerves. It need scarcely be 

 emphasized that connections of this kind also exist between this center 

 and other motor paths. 



1 Sachs. Gesellsch. der Wissensch., 1904. 



2 Ergebn. der Physiol., 1907. 



3 Archiv fur Ophthalm., Ivii, 1904, 363. 



