298 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



proper and unique pattern of the species, and you begin to have 

 some idea of the wonders of this universe. 



When you lift your arm or bend your finger the process is an 

 electrochemical one. The nerve impulse from the brain sets up at 

 the proper places in the muscles an electrically induced chemical 

 alteration. It is possible that the genes do their work in the same 

 way ; we do not know. 



Nothing is more mysterious in this whole complex story than that 

 the genes, and the tissues and glands which they help to build up, seem 

 to work on an elaborate and intricate time schedule. In human 

 beings, for example, there are characteristics that do not develop 

 until many years have passed. There appear to be "bad" genes, from 

 the individual's point of view, which lurk unsuspected for half a cen- 

 tury and then cause a man to become bald in just the way his father 

 did. Others seemingly wait for decades to produce hereditary blind- 

 ness or insanity. A marvelous mechanism is that operated by the 

 gonads which brings about the characteristics of adolescence at 13 or 

 14, produces hair on the face of the male (in certain races) at 18 or 19, 

 and either creates the changes of the menopause in the forties and 

 fifties or, by ceasing to function, permits them. There are even pre- 

 sumably old-age genes which determine, before you are born, how 

 long you will live — if you don't terminate your life prematurely with 

 whiskey, a bullet, or a speeding automobile. For longevity, as every- 

 one knows, "runs in families," and whatever runs in families, if 

 actually inherited, is controlled by the genes. That is to say, the 

 tissues and organs of the individual have a gene-determined life cycle 

 that will be carried out if other factors do not intervene. 



The miracle of the "time-clock genes" is clearly shown in the case 

 of identical twins — twins which arise from a single fertilized egg 

 which for some reason divided early in embryonic life to produce two 

 human beings with, so far as science knows, the same genes and 

 chromosomes. Identical twins develop the same physical character- 

 istics, throughout life, at almost exactly the same time. This prin- 

 ciple holds even if three, four, or five children have developed from 

 a single egg. This is the case with the Dionne quintuplets, who have 

 the same genes. 



Let me emphasize again that it is wrong to think of a single gene 

 as performing a specified function unaided. It is now believed that 

 every gene influences every other, just as all the genes occur in every 

 chromosome and there are 48 chromosomes in every cell of the body 

 except the sperm and ovum from which the new life will be created. 

 There are eye genes in your toe, and toe genes in your eye. Science 

 now knows that there are certain groups of genes which are inherited 



