EFFECT OF ENVIRONMENT ON INHERITANCE 313 



How the genes behave is a problem of heredity. Experience 

 has shown, that as a result of selection it is possible not only to 

 maintain the quality of the stock, but also to improve it, up to a 

 certain point. Wherever selection is neglected, the cultivated 

 plants or domestic animals deteriorate in quality. They deteri- 

 orate whenever the food or any living condition is neglected. 

 The rule of the successful breeder is to select animals or plants 

 showing the best ancestry. Then he should provide the best con- 

 ditions for their healthy growth and development. 



Effect of environment on ancestral traits.' An unborn child may 

 be influenced by conditions prevailing in either parent. Malnu- 

 trition or serious ill-health on the part of the mother has an injurious 

 effect on the offspring. Severe shock or grief, worry, nervous 

 exhaustion, the influence of a very few diseases, lead, mercury, or 

 alcohol poisons in the blood or tissues may act detrimentally on 

 the unborn offspring. The effect of these conditions or materials 

 is to interrupt the proper nutrition of the offspring, directly poison 

 it, or, by generating toxins in the mother, poison the developing 

 embryo. Disease- toxins affect unborn children to such an extent 

 as to sometimes cause malformations, arrested development, 

 instabilities of the nervous system, general physical or mental 

 weaknesses, or even death before birth. The children of inebriates 

 comprise a striking proportion of criminals, imbeciles, and those 

 with predispositions toward certain diseases. All of these effects 

 are environmental effects, not inherited effects. The character of 

 the environment of the child before and after birth is a factor 

 of great importance in the development of the child. 



Many prospective mothers think they can develop musical 

 ability in a child by studying and playing music before the child 

 is born. Or they hope they may produce beauty in the child by 

 long contemplation of a picture of a beautiful child. The expla- 

 nation frequently given for birthmarks is that the mother ate 

 many strawberries or tomatoes before the child was born or she was 



WH. FITZ. AD. BIO. 21 



