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 



