20 THE TRESENT CONDITION 



a small fraction of a 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 smaller tube the spinal 

 marrow and brain are fashioned ; in the lower, the ali- 

 mentary canal and heart, and at length two pairs of 

 buds shoot out at the sides of the body, which are the 

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

 section of the embryo in this state would in all essen- 

 tial 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 metamorphosed 

 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 at each 

 of these complex structures that we have mentioned. 

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

 ditions. This diagram represents the embryo of a dog ; 

 and I should tell vou that there is a time when the 



m 



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

 monkey, nor man, can be distinguished by any essen- 

 tial feature one from the other ; there is a time when 

 they each and all of them resemble this one of the Dog. 

 But as development advances, all the parts acquire 

 their speciality, till at length you have the embryo 

 converted into the form of the parent from which it 



