of the Organic Systems of Vegetables. 101 



the roots, and its passage upwards through the stem into the 

 leaves : it also must have much influence in changing and 

 overcoming the chemical attractions of the elements of vege- 

 table food, and seems to be one great agent in the curious 

 process of vegetable assimilation. 



CONTRIBUTIONS TO THE PHYSIOLOGY OF VISION. 



No. I. 



UNDER the above title it is proposed to bring forward those 

 stores of knowledge on this subject which have been hitherto 

 locked up in the repositories of foreign scientific literature. 

 The physiology of vision has a peculiar claim on the atten- 

 tion of philosophers, as presenting some of those links which 

 connect physical with mental phenomena. Metaphysicians, 

 physiologists, natural philosophers, and artists, have equally 

 made it an object of their study ; and the names of Bap- 

 tista Porta, Leonardo da Vinci, Kepler, Descartes, Newton, 

 Berkeley, Reid, Buffon, Darwin, Wells, Brown, Young, &c., 

 are among those who have advanced the inquiry by their in- 

 vestigations and discoveries. That the subject is of such equal 

 interest to so many different classes of inquirers, is perhaps 

 the cause that, as a whole, it is so imperfectly known. Each 

 person who occupies himself with its study, looking at it only 

 from his own point of view, disregards those facts which he 

 considers as belonging to the province of others, and thus 

 is unable to arrive at those general conclusions which can 

 only be obtained from a complete survey of all the vari- 

 ous phenomena and their relations. To render some assist- 

 ance towards forming a more complete theory of vision, we 

 shall successively give an account of the discoveries of Pur- 

 kinje, Goethe*, Mile, Miiller, Plateau, &c. The number 

 of these interesting memoirs on this interesting branch of 

 science, which have been entirely unnoticed in ^ this country, 



* An account of the ' Farbcnlehre,' or theory of colours, of this illustrious poet 

 and philosopher, will form ouo of the subsequent papers of this series. 



