IMAGINATION. 71 



down the optic nerve in Mej^er's and Fere's negative after- 

 image. Therefore it can flow backward ; therefore it may 

 flow backward in some, however slight, degree, in all imag- 

 ination.* 



To 2) : The difference alleged is not absolute, and sensa- 

 tion and imagination are hard to discriminate where the 

 sensation is so weak as to be just perceptible. At nioht 

 hearing a very faint striking of the hour by a far-off clock, 

 our imagination reproduces both rhythm and sound, and it 

 is often difficult to tell which was the last real stroke. So 

 of a baby crying in a distant part of the house, we are un- 

 certain whether we still hear it, or only imagine the sound 

 Certain violin-players take advantage of this in diminuendo 

 terminations. After the pianissimo has been reached 

 they continue to bow as if still playing, but are careful not 

 to touch the strings. The listener hears in imagination a 



* It seems to also flow backwards in certain hypnotic Lalluciuations. 

 Suggest to a ' Subject ' in tlie hypnotic trance that a sheet of paper has a 

 red cross upon it, then pretend to remove the imaginary cross, whilst you 

 tell the Subject to look fixedly at a dot upon the paper, and he will pres- 

 ently tell you that he sees a ' bluish-green 'cross. The genuineness of the 

 result has been doubted, but there seems no good reason for rejecting M. 

 Binet's account (LeMaguetisme Animal, 1887, p. 188). M. Binet, following 

 M. Parinaud, and on the faith of a certain experiment, at one time believed, 

 the optical brain-centres and not the retina to be the seat of ordinary nega- 

 tive after-images. The experiment is this : Look fixedly, with one eye 

 open, at a colored spot on a white background. Then close that eye and 

 look fixedly with the other eye at a plain surface. A negative after-image 

 of the colored spot will presently- appear. (Psychologie du Raisonuement, 

 1886, p. 45.) But Mr. Delabarre has proved (American Journal of Psy- 

 chology, II. 326) that this after-image is due, not to a higher cerebral pro- 

 cess, but to the fact that the retinal process in the closed ej^e affects 

 consciousness at certain moments, and that its object is then projected 

 into the field seen by the eye which is open. M. Binet informs me that 

 he is converted by the proofs given by Mr. Delabarre. 



The fact remains, however, that the negative after-images of Herr Meyer, 

 M. Fere, and the hypnotic subjects, form an exception to all that we know 

 of nerve-currents, if they are due to a refluent centrifugal current to the 

 retina. It may be that they will hereafter be explained in some other way. 

 Meanwhile we can only write them down as a paradox. Sig. Sergi's theory 

 that there is alicays a refluent wave in perception hardly merits serious con- 

 sideration (Psychologie Physiologique, pp. 99, 189). Sergi's theory has 

 recently been reatfirmed with almost incredible crudity by Lombroso and 

 Ottolenghi in the Revue Philosophique, xxix. 70 (Jan. 1890). 



