20 HISTORY OF 



are produced the soonest, and appear the most 

 prominent. It is true, indeed, that in viviparous 

 animals, and particularly in man, they are not so 

 large in proportion, at first, as in the oviparous 

 kinds j nevertheless, they are more speedily de- 

 veloped, when they begin to appear, than any 

 other parts of the body. It is the same with the 

 organ of hearing : the little 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 begun, and the most com- 

 pletely finished. 



If we examine the eyes of a child some hours, 

 or even some days after its birth, it will be easil) 

 discerned that it, as yet, makes no use of them. 

 The humours of the organ not having acquired 

 a sufficient consistence, the rays of light strike 

 but confusedly upon the retina, or expansion o: 

 the nerves at the back of the eye. It is not til 

 about a month after they are born, that childrer 

 fix them upon objects ; for, before that time 

 they turn them indiscriminately every where 

 without appearing to be affected by any. A 

 six or seven weeks old, they plainly discover ; 

 choice in the objects of their attention j they fb 



