3j0 histohy of 



the body. It is the same with the organ of hearing ; tlic Iittla 

 bones that compose the internal parts of the ear are entirely 

 formed before the other bones, though much larger, have acquired 

 any part of their growth or solidity. Hence it appears, that 

 those parts of the body which are furnished with the greatest 

 quantity of nerves, are the first in forming. Thus the brain and 

 the spinal-marrow, are the first seen begun in the embryo ; and, 

 in general, it may be said, that wherever the nerves go, or send 

 their branches in great numbers, there the parts are soonest be- 

 gun, and the most completely finished. 



If we examine the eyes of a child some hours, or even some 

 days after its birth, it will be easily discerned that it as yet makes 

 no use of them. The humour of the organ not having acquired 

 a sufficient consistence, the rays of light strike but confusedly 

 upon the retina, or expansion of nerves at the back of the eye. 

 It is not till about a month after they are born, that children fix 

 them upon objects ; for, before that time, they turn them indis- 

 criminately everywhere, without appeai-ing to be affected by 

 any. At six or seven weeks old, they plainly discover a choice 

 in the objects of their attention ; they fix their eyes upon the 

 most brilliant colours, and seem peculiarly desirous of turning 

 them towards the light. Hitherto, however, they only seem to 

 fortify the organ for seeing distinctly ; but they have still many 

 illusions to correct. 



The first great error in vision is, that the eye inverts every 

 object : and it in reality appears to the child, until the touch 

 has served to undeceive it, turned upside down. A second eri'or 

 in vision is, that every object appears double. The same object 

 forms itself distinctly upon each eye ; and is consequently seen 

 twice. This error, also, can only be corrected by the touch ; 

 and although, in reality, every object we see appears inverted 

 and double, yet the judgment and habit have so often corrected 

 the sense, that we no longer submit to its imposition, but see 

 every object in its just position, the very instant it appears. 

 Were we therefore, deprived of feeling, our eyes would not only 

 misrepresent the situation, but also the number, of all things 

 around us. 



To convince us that we see objects inverted, we have only to ob- 

 serve the manner in which images are represented, coming through 

 A small hole in a darkened room. If such a small hole be made in a 



