3io Animal Life and Intelligence. 



tions of organized beings, from data given by sight, touch, 

 and the muscular sense. It is true that I can now estimate 

 the distance of the house without going to it ; but my eyes 

 go to it, and I can feel them go. The panes of my window 

 are separated by iron bars. As I look from them to the 

 distant house and back to them again, I can feel my eyes 

 going from one to the other. The lens of the eye is 

 adjusted for near or far distance by the action of a ciliary 

 muscle, through which its anterior surface can be flattened, 

 returning again by its own elasticity to the more convex 

 form when the muscle ceases to act. Each eye, moreover, 

 is moved in its orbit by six eye-muscles, and in normal 

 vision the two eyes act as one organ. For near distances 

 they converge ; for far distances there is less convergence. 

 Through the muscular sense, which is here extraordinarily 

 delicate, we can feel the amount of accommodation and 

 convergence ; and thus we can feel the eyes going to or 

 coming from a near and a distant object. Of course, we 

 are aided in judging or estimating distances by the apparent 

 size of the object when the real size is known, by the 

 clearness of its outlines in a slightly hazy atmosphere, and 

 so forth. But apart from sufn judgments, it would pro- 

 bably be impossible to perceive that an object is near or 

 distant in the absence of muscles of accommodation and 

 convergence affording the data of the muscular sense. Not 

 only the distance of two objects from the eye, but their 

 distance apart, can be measured by the aid of the muscular 

 sense as we move the eyes from one to the other. And in 

 us this is so delicate that, according to Weber, a distinct 

 muscular sensation is attached to a displacement of a 

 sensitive point of the yellow spot through less than ^^ 

 of an inch. 



Now, if it be true that the consciousness aroused by 

 objects around us, through sensation, is an accompaniment 

 of certain physiological changes in the brain, it is clear 

 that the localization of their points of origin in special 

 parts of the skin, and the outward projection of the objects 

 exciting vision, is an act of the mind quite distinct from 



