Profound and entertaining demonstrations that the eyes have it

It should be made clear at the outset that, despite its title, A Natural History of Vision is not a history in any conventional sense. Rather, it is a collection of quotations from people who have been concerned in one way or another with human vision. Furthermore, it ends rather arbitrarily at about 1840, thereby missing the rapid growth in our understanding of vision that has taken place since then.

While many of the quotations are profound, and some entertaining, the majority are no longer than a sentence, and many are even shorter. Taken out of context in this way, they would make little sense to a reader who was not familiar with the history of visual science. To be fair, Nicholas Wade begins each chapter with a short explanation of what is to follow, but these explanations are too compact, and often too technical, to be readily accessible to the general reader. They also tend to be descriptive, rather than explanatory: as an example, in the chapter on colour vision, no mention is made of the difference between additive colour mixture (the mixture of coloured lights) and subtractive colour mixture (mixtures of pigments). This distinction, which vexed those who were interested in vision for several centuries, is responsible for apparent contradictions among the quotations. (Curiously, Wade does explain the difference in his final summary chapter; but it would have been more useful in the chapter on colour.)

An attractive feature of the book is the numerous illustrations: portraits of most of the authors cited are shown. Cutting away all but the head saves space and makes the presentation more uniform, but at the expense of slighting the artists who created the prints. Wade also makes effective use of illustrations of early experimental equipment. Unfortunately, the quality of reproduction varies greatly, apparently reflecting differences among the originals, but some could profitably have been retouched.

Wade has divided vision into seven topics, which are treated separately. This was presumably intended to make the material more accessible to the non-specialist reader, but it has the unfortunate consequence of obliterating areas in which different topics overlap. The emphasis given to various topics is bound to be a matter of personal taste, but I would have preferred that less space had been given to binocular vision, including the old chestnut of why, although we have two eyes, we see single objects. Chapter prefaces are generally accurate, but there are curious lapses: in the introduction we are told that the English translation of Helmholtz's Physiological Optics was made from the 1867 edition. In fact, as far as Wade knows (he has written elsewhere about this), it was made from the third edition, produced by a committee half a century later, after Helmholtz's death. Similarly, it is remarkable to find someone as conversant with art as Wade is rendering the medieval Italian artist Tommaso da Modena "Moderna". But these are minor points, and compensated by such charming passages as Benedetto Castelli advising the reader, in order to form an after-image, to gaze at an object "for as much time as it takes to say the Miserere psalm". If there is one impression that keeps surfacing throughout the book, it is how remarkably many visual phenomena were described by ancient writers, and how ingenious many of the early observers were.

Research on the visual system has become a serious industry: the 1999 meeting of the Association for Research in Vision and Ophthalmology attracted over 5,000 presentations, and this is only one of many. Considering this, it is remarkable that there is no comprehensive modern written history of vision. If there were, Wade's book would be a useful companion, but not a substitute for it.

C. R. Cavonius is at the University of Dortmund, Germany.