102 Contributions to the Physiology of Vision. 



might surprise us, did we not know that the same neglect 

 extends to many other important departments of knowledge. 



* Beitrage zur Kenntniss des Sehens in subjectiver Hinsicht, 

 etc.* (Essay on the Subjective Phenomena of Vision, by Dr. 

 J. Purkinje, Professor of Physiology at the University of 

 Breslau.) Prague. 1823. 



This little volume has excited considerable interest in Ger- 

 many ; it relates to those appearances which, independently of 

 external objects, are perceived in the organ of sensation itself. 

 To distinguish these phenomena from those which arise on the 

 presence of their appropriate external objects, the author em- 

 ploys the term subjective, which, as denoting this class of 

 phenomena better than any other we are acquainted with, and, 

 to avoid circumlocution, we have purposely retained : it will, 

 however, on consideration, be perceived, that the term is not 

 strictly proper, as, correctly speaking, all phenomena, as such, 

 are subjective, i. e. in the mind ; and were we, without quali- 

 fication, to admit the classification of phenomena into objective 

 and subjective, we should be unable to determine, with any 

 degree of accuracy, where the objective ends or the subjective 

 begins. Thus, the vessels of the eye arid the retina itself are 

 subjective, considered as parts of the visual organ ; yet we 

 shall see that in some of Dr. Purkinje's experiments they be- 

 come real objects, and are perceived as such. But we shall 

 not further discuss this question ; what we have said will be 

 sufficient to explain the term subjective as employed by Dr. 

 Purkinje and by ourselves in the following extracts. We now 

 proceed to an abridged description of the most interesting of 

 Dr. Purkinje's experiments. 



I. Luminous Figures produced by rapid alternations of Light 

 and Shade. These figures are most distinctly seen in the 

 following manner: the eye-lids being closed and the eyes 

 directed towards the sun, the observer quickly moves his hand 

 with the fingers spread, from one side to the other, so that the 

 luminous rays are alternately intercepted and admitted ; at 

 the beginning of the experiment a yellowish-red glare is per- 

 ceived which is afterwards replaced by a beautiful and regular 

 figure, which it is, however, impossible to fix or determine, 



