XI PHENOMENA OF ORGANIC NATURE 319 



grain in weight, undergoes a series of changes, 

 wonderful, complex changes. Finally, upon its 

 surface there is fashioned a little elevation, which 

 afterwards becomes divided and marked by a 

 groove. The lateral boundaries of the groove 

 extend upwards and downwards, and at length 

 give rise to a double tube. In the upper and 

 smaller tube the spinal marrow and brain are 

 fashioned ; in the lower, the alimentary canal and 

 heart ; and at length two pairs of buds shoot out at 

 the sides of the body, and they are the rudiments 

 of the limbs. In fact a true drawing of a section 

 of the embryo in this state would in all essential 

 respects resemble that diagram of a horse reduced 

 to its simplest expression, which I first placed 

 before you (Fig. 1). 



Slowly and gradually these changes take place. 

 The whole of the body, at first, can be broken up 

 into "cells," which become in one place meta- 

 morphosed into muscle, in another place into 

 gristle and bone, in another place into fibrous 

 tissue, and in another into hair ; every part 

 becoming gradually and slowly fashioned, as if 

 there were an artificer at work in each of these 

 complex structures that I have mentioned. This 

 embryo, as it is called, then passes into other con- 

 ditions. I should tell you that there is a time when 

 the embryos of neither dog, nor horse, nor porpoise, 

 nor monkey, nor man, can be distinguished by any 

 essential feature one from the other; there is a 



