116 BIOLOGICAL ASPECTS OF HUMAN PROBLEMS 



there is a large territory where the material and the 

 psychical overlap. We may consider first the in- 

 jurious agents that affect the body, and then those 

 that affect the mind. 



Damage to the body mechanism may arise in 

 many ways. It may occur very early in the life of 

 the individual, in fact, previous to birth. Disease 

 in father or mother may act so injuriously on the 

 germ plasm as to affect the embryo in a hurtful 

 manner, and mortgage its future; and a similar 

 result may follow from acute or chronic poisoning 

 of the germ plasm of either parent. These con- 

 genital influences are capable of showing themselves 

 in many ways, in malformations, gross defects, 

 tumors (including cancer), and in a predisposition 

 to diseases such as gout, diabetes, epilepsy, insanity, 

 and other nervous disorders. Yet important as are 

 these congenital injurious influences, they are of far 

 less moment than those harmful effects operating on 

 the individual after birth. The entry of the child 

 into the world marks the beginning of a struggle 

 against unfriendly forces which lasts until death. 

 Not only must the new being face the many possi- 

 bilities of mechanical accident, but it has lying in 

 wait for it a host of minute living enemies in the form 

 of bacteria and other microorganisms. In order 

 that these latter agents of injury should be success- 

 ful against their human antagonists, they must not 

 merely find a portal of entry into the body (as 

 through the lungs or stomach, or eyes or ears, or 



