422 NATURE AND MAN. 



action ; and in proportion as each kind of functional activity 

 becomes limited to a particular organ, does the mutual depend- 

 ence of the several parts of the organism necessarily become more 

 intimate. With this functional limitation we commonly find an 

 increasing complexity of structure, which enables the function to 

 be more effectively performed; and thus the body of any "highly 

 organized " animal consists of a number of dissimilar organs, each 

 — like the several parts of the Walter press — doing its own proper 

 work, but thereby contributing, at the same time, to maintain the 

 activity of the rest. 



It has been on this marked adaptiveness of particular organs 

 to the kinds of action they respectively perform, that the " argu- 

 ment from design " has been commonly based ; and no case of 

 this adaptation has been more frequently dwelt upon, as showing 

 in its perfection the most obvious and convincing evidence of 

 " design " than the human eye. The perfection of this adaptation, 

 however, has been partially denied by several modern writers, who 

 have based their denial on a statement contained in a most 

 interesting and instructive lecture on "Tiie Eye and Vision," 

 given some years ago by my very distinguished friend. Professor 

 Helmholtz.* The first part of this lecture is devoted to an ex- 

 position of the structure and actions of the eye, considered merely 

 as an optical instrument, and of those more recent researches, 

 which have shown that, in addition to retinal defects previously 

 known, the eye is not perfectly corrected for either spherical or 

 chromatic aberration, that the crystalUne lens has by no means the 

 perfect clearness it has been supposed to possess, and that its 

 fibrous structure produces an irregular radiation in the image of 

 any single bright point. " Now, it is not too much to say," con- 

 tinues the lecturer, " that if an optician wanted to sell me an 

 "instrument which had all these defects, I should think myself 

 "quite justified in blaming his carelessness in the strongest terms, 

 "and giving him back his instrument." f 



Every one who has any knowledge of theological controversy, 

 will recollect how frequendy the charge has been justly raised of 



• " Popular Lectures on Scientific Subjects." Translated by Dr. Atkinson, 

 London, 1873. 

 t Ibid., p. 219, 



