INFLUENCE OF LIGHT. 153 



That which sees will never itself be visible. The 

 secret principle of sensation, the mystery of the life 

 that is in us, will never be unfolded to finite minds. 



Numerous experiments have been made from time to 

 time on the influence of light upon animal life. It has 

 been proved that the excitement of the solar rays is too 

 great for the healthful growth of young animals ; but, 

 at the same time, it appears probable that the develop- 

 ment of the functional organs of animals requires, in 

 some way, the influence of the solar rays. This might, 

 indeed, have been inferred from the discovery that 

 animal life ceases in situations from which light is 

 absolutely excluded. The instance of the Proteus of the 

 Illyrian lakes may appear against this conclusion. This 

 remarkable creature is found in the deep and dark 

 recesses of the calcareous rocks of Adelsburg, at Sittich ; 

 and it is stated, also in Sicily, and in the Mammoth caves 

 of Kentucky. Sir Humphry Davy describes the Proteus 

 anguinus as " an animal to whom the presence of light 

 is not essential, and who can live indifferently in air and 

 in water, on the surface of the rock, or in the depths of 

 the mud/' The geological character of rocks, however, 

 renders it extremely probable that these animals may 

 have descended with the water, percolating through 

 fissures from very near the surface of the ground. All 

 the facts with which science has made us acquainted 

 and both natural and physical science has been labour- 

 ing with most untiring industry in the pursuit of truth 

 go to prove that light is absolutely neccessary to 

 organization. It is possible the influence of the solar 

 radiations may extend beyond the powers of the human 

 senses to detect luminous or thermic action, and that 



may arise from the seusorial perception of actual changes in pro- 

 gress in the physical state of that organ itself subsequent to the 

 cessation of the direct stimulant." On the action of the Rays of 

 the Solar Spectrum on Vegetable Colours, fyc. : by Sir J. F. W. 

 Herschel, Bart. 



