398 HUMAN PHYSIOLOGY 



sessed such strength as an emergency required. So they 

 afford ground for confidence that our children will find 

 themselves as well equipped for duty. If, on the other 

 hand, we have to confess to many failures and unwise 

 choices, we need not think that the stock we represent is 

 much worse because of our sorry performances than it was 

 at the outset. But we are bound to admit that it has not 

 turned out to be a good strain, and we face the serious 

 question as to whether it deserves to be perpetuated. Un- 

 fortunately the people who most need to ask this question 

 are the least likely to do so. 



This matter-of-fact account of human reproduction has 

 done scant justice to the wonder of the process. The mys- 

 tery of it has been oppressively felt, even from the day 

 when the Psalmist wrote, "Thine eyes did see my sub- 

 stance, yet being unperfect; and in thy book all my mem- 

 bers were written, which in continuance were fashioned, 

 when as yet there was none of them" (Psalm CXXXIX, 

 16). Two minute bits of living matter are united, and 

 from the time of their union they are able to mould to a 

 certain type of organization an increasing mass of material. 

 Eventually the new organism is so large that the ovum and 

 sperm seem infinitesimal by comparison, but their stamp 

 is on its every part; they have "leavened the whole lump." 

 And within the maturing body there are already set apart 

 the representative cells of the new blending, different in 

 their capacities from all other germinal elements that 

 have ever lived. 



The student always feels like asking how such potential- 

 ities can be compressed into the microscopic compass of 

 the egg or the still smaller sperm. No one can pretend to 

 consider that this is an easy conception. We may, never- 

 theless, make the fact seem more reasonable if we make al- 

 lowance for the possibilities of what is called by the organic 

 chemist stereo-isomerism. The master of this difficult 

 subject well knows that numerous compounds with clearly 

 individual properties may exist, even though all the mem- 

 bers of the series have the same composition as deter- 



