42 PSYCHOLOGY. 



see a page of Chinese print but it suggests nothing to us. 

 A hemiopic disturbance of vision is one in which neither 

 retina is affected in its totality, but in which, for example, 

 the left portion of each retina is blind, so that the animal 

 sees nothing situated in space towards its right. Later 

 observations have corroborated this hemiopic character of 

 all the disturbances of sight from injury to a single hemi- 

 sphere in the higher animals ; and the question whether 

 an animal's api)arent blindness is sensorial or only psychic 

 has, since Munk's first publications, been the most urgent 

 one to answer, in all observations relative to the function of 

 sight. 



Goltz almost simultaneously with Ferrier and Munk 

 reported experiments which led him to deny that the 

 visual function was essentially bound up with any one 

 localized portion of the hemispheres. Other divergent 

 results soon came in from many quarters, so that, without 

 going into the history of the matter any more, I may report 

 the existing state of the case as follows : * 



In fishes, frogs, and lizards vision persists when the 

 hemispheres are entirely removed. This is admitted for 

 frogs and fishes even by Munk, who denies it for birds. 



All of Munk's birds seemed totally blind (blind senso- 

 rially) after removal of the hemispheres by his operation. 

 The following of a candle by the head and winking at a 

 threatened blow, which are ordinarily held to prove the 

 retention of crude optical sensations by the lower centres 

 in sujDposed hemisphereless pigeons, are by Munk ascribed 

 to vestiges of the "vdsual sphere of the cortex left behind 

 by the imperfection of the operation. But Schrader, who 

 operated after Munk and with every apj^arent guarantee of 

 completeness, found that all his pigeons saw after two 

 or three weeks had elapsed, and the inhibitions resulting 

 from the wound had 23assed away. They invariably avoided 

 even the slightest obstacles, flew very regularly towards 

 certain perches, etc., differing toto ccelo in these resj)ects 

 with certain simply blinded pigeons Avho were kept with 



* The history up to 1885 may be found in A. Christiani : Zur Physi- 

 ologie des Gebirues (Berlin, 18»5). 



