556 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



nations in 120 alcoholic and nonalcoholic human beings, was able to 

 demonstrate very clear differences, and to assert that " the hurtful 

 influence of chronic alcoholism upon sexual glands is not to be 

 denied." Similar results have been obtained with other poisons; 

 and during recent years it has also been shown that germ variations 

 may be induced by temperature (Sumner, Bordage, Tower) and by 

 the injection of chemicals into the immature ovary (Macdougal). 

 Finally, from inquiries which I have lately made into the effect of 

 X rays, there seems to be no doubt that males working with unpro- 

 tected tubes are rendered temporarily sterile owing to the action of 

 the rays upon the sperm cells. If this and other agencies can thus 

 bring about the death of the germ cell, it is a justifiable inference 

 that smaller doses can so injure it as to produce a living but impaired 

 offspring; and the earlier observations above quoted show that this 

 is actually the case. 



In view of the evidence which is now available and is daily 

 increasing, it is impossible to deny that the germ cells may be 

 adversely affected by the environment. As to the actual causal 

 agents of this change in human beings our knowledge is still in- 

 complete. My own observations lead me to think that alcoholism, 

 tuberculosis, and venereal diseases play an important part. But 

 there may be many others with which we are as yet unacquainted, 

 and which will certainly be brought to light when once we discard 

 the bogey of "spontaneous variation," and seek them in a true scien- 

 tific spirit, devoid of preconceived notions as to what may be possible 

 and what impossible. 



The important question now arises as to the nature of the germinal 

 change which is thus induced. In spite of the many researches of 

 recent years, we still know very little about the physical basis of 

 inheritance; but this much is certain, that, in some at present 

 mysterious way, the germ cell contains "representatives" or "de- 

 terminants " of all the variable parts of the body of the offspring to 

 which it subsequently gives rise. Perhaps the best way of regard- 

 ing these is that of a series of directive forces or specific energies, 

 each of which is concerned with directing the growth of a particular 

 tissue. On this hypothesis we may assume that the effect of toxic 

 agents is to reduce this innate potentiality, and to bring about what 

 may be termed a devitalization, or an impairment of the whole, or 

 of certain specific, energies of the germ cell. This will not only be 

 operative in the case of the immediately resulting offspring, but, 

 since it is fundamental, may involve subsequent generations. This 

 is in nowise antagonistic to the view of germ continuity. 



But the different organs of the human body, as they exist to-day, 

 vary greatly in what may be called their antiquity. There are 

 some — for instance, the circulatory system — which have undergone 



