SIGHT. 591 



muscles, while the converging motions are regulated by the 

 oblique. The experiments from which Sir C. Bell infers that 

 the oblique are not voluntary muscles prove only that their 

 functions are not the same as those of the straight muscles. If 

 Professor Wheatstone is correct in the functions which he assigns 

 to the oblique muscles, it is easy to see that they have an appro- 

 priate office under voluntary control, though their peculiar ac- 

 tions do not assist the straight muscles. 



Light, like heat, is an agent by which all vegetables and animals are intended 

 to be influenced. As the terms heat and cold are only relative, and no tem- 

 perature is so low but that there might be a lower, and the plant, which lives 

 in the snow only of polar regions, would still perish if the temperature were 

 lower than it is ; so light really exists in darkness, no darkness might not be 

 darker, and no plant or animal can be totally deprived of light. Deprived of 

 light, a plant would lose its characteristic form, colour, taste, and odour, and 

 puzzle the best botanist : persons deprived of light grow pale and sickly ; but 

 in this case, whether the place be a mine, a narrow street, or a prison, the want 

 of fresh air, and in regard to prisoners the -depressed condition of the mind, and 

 occasionally the deficiency or bad quality of food, must also be taken into con- 

 sideration : and, if pregnant women confined in dungeons often produce mon- 

 sters, the state of mind cannot but be a powerful cause of the aberration. Dr. 

 Edwards has proved that, by excluding tadpoles from the light, they will grow to 

 double or triple the size that tadpoles usually attain, but are not metamorphosed 

 into frogs. He thinks that the proteus anguinus, which, like tadpoles, has lungs 

 and gills, is but the first stage of an animal which is prevented from becoming 

 perfect by inhabiting the subterraneous waters of Carniola. He concludes there- 

 fore that light has a great influence upon the human body ; and ascribes the 

 observation of Humboldt, that, among millions of Caribs, Mexicans, Peru- 

 vians, &c., not one instance of deformity appeared, to the exposure of their body 

 to light, and much of the sickliness of imprisoned persons and scrofulous children 

 living in close streets to the want of light. (De V Influence, <$-c. P. iv. c. 15.) 

 " Vegetables, though they have no nerves, guided by light, open and close their 

 flowers and their leaves." " In plants with compound leaflets," says Professor 

 Lindley, " the leaflets fold together while the petiole is recurved at the approach 

 of night ; and the leaflets again expand and raise themselves at the return of 

 day. In others the leaves converge over the flowers, as if to shelter those more 

 delicate organs from the chill air of night. The flowers of the crocus and similar 

 plants expand beneath the bright beams of the sun, but close as soon as these are 

 withdrawn. The cenotheras unfold their blossoms to the dews of evening, and 



R R 



