December 2, 1898.] 



SCIENCE. 



795 



invention, the oplithalmoscope. The parts then 

 began to appear more slowly, at intervals of 

 about two years, until the death of von Helm- 

 holtz in 1894. The eighth part had then been 

 completed, extending the work to page 64.5. 

 The part on sensations of light runs from 

 page 231 to page 575, being enlarged by more 

 than one hundred pages. Much new material, 

 especially work on intensity done in von Helm- 

 holtz's laboratory, is here added. The final 

 part, on perceptions and judgments, mostly 

 edited by Professor Konig after the death of 

 von Helmholtz, has scarcely been altered. 

 Professor Konig states that it was not the 

 author's intention to make many changes in 

 this part, even had he been able to continue the 

 revision. The work concludes with an index 

 of the literature, containing 7,833 titles, com- 

 piled by Professor Konig. 



It seems ungracious to do other than accept 

 this new edition of a master work with sincere 

 thankfulness. Even though it may not as com- 

 pletely represent contemporary knowledge of 

 the sense of sight as did the first edition, thirty 

 years ago, ought we not to be truly grateful to 

 the author for his elaborate revision ? Grateful 

 we should doubtless be and appreciative of the 

 heroic effort of von Helmholtz. But we owe 

 truth to the dead, and I must state my own 

 view to be that little or nothing, or worse than 

 nothing, has been accomplished by this revision. 

 It has happened in cases other than this that a 

 classic work making a remarkable contribution 

 to science has ultimately become an obstacle to 

 to the advance of science. Kant creates a 

 work on epistemology that alters the entire 

 groundwork of metaphysics. After a hundred 

 years we find the cry prevalent in Germany 

 ' back to Kant,' and back they go, not only to the 

 Critique as representing the best thought of the 

 eighteenth century, but as though all its trivi- 

 alities were of contemporary importance. 



The Physiologische Optik, the publication of 

 which was begun in 1856 and completed in 

 1867, is one of the few classics in the history of 

 science. It summarized the existing state of 

 knowledge with rare completeness and lucidity, 

 and made remarkable original contributions to 

 the advancement of knowledge. But a work of 

 such magnitude and genius actually prevents 



the preparation of new books truly reflecting 

 the present conditions and conflicting claims of 

 facts and theories. The physicist, the physi- 

 ologist, even the psychologist, is apt to regard 

 the gospel according to Helmholtz as infallible. 

 This is the inevitable, against which even 

 the gods do not contend. But the publica- 

 tion of a new edition dated 1896 tends need- 

 lessly to prop up the Procrustean bed, confining 

 the growing members. Since 1860 the doctrine 

 of evolution has been established ; since I860- 

 modern psychology has been developed. The 

 ' 1896 ' on the title-page is harmful to science ; 

 unfair to von Helmholtz himself 



Even the title of the book is an anachronism. 

 Physiological optics correctly describes only that 

 part concerned with the eye as an optical instru- 

 ment. Optics is a department of physics and no 

 longer includes the psychological phenomena 

 of vision. When von Helmholtz himself pre- 

 pared a little later a work on the sense of hear- 

 ing, in many ways a companion volume to that 

 on vision, he did not call it Physiologische Akous- 

 tik, but Tonempfindungen. The literature on 

 vision prior to 1867 is small compared with that 

 subsequent. Thus on the perception of color 

 163 titles are given in Professor Konig' s bibli- 

 ography as published earlier than 1867, and 1034 

 between that and 1894. The newer literature 

 is scarcely incorporated, and in so far as this is 

 attempted a false perspective is given by devot- 

 ing many pages to work done by Professor Konig, 

 Dr. Brodhun and others in von Helmholtz's 

 laboratory, while work of equal importance 

 done elsewhere is ignored. The injustice done, 

 for example, to Hering, is very great. In vari- 

 ous points of conflict von Helmholtz replies to 

 Hering, but in such an inadequate fashion as to 

 show either carelessness or a complete lack of 

 appreciation of the value of evidence. The pos- 

 sibility that he might be wrong or that progress 

 had been made seems scarcely to occur to him. 



I may note two of these points of difference 

 between Hering and von Helmholtz — the per- 

 ception of color and the perception of space — ■ 

 to illustrate the tenacity with which von Helm- 

 holtz clung to his early views in spite of ac- 

 cumulating evidence against them. TheYoung- 

 Helmholtz theory of color-vision is well known, 

 being, in fact, imposed annually as ascertained 



