TYPES OF MEN 275 



in a thousand ways, physical and social. Types are easy to recognize, 

 but hard to measure. We use many uncertain characteristics to dis- 

 tinguish them, and yet must expect that any one of them will fail if it 

 is put to a definite test. 



Some changes, however, are true variations due to the evolution of 

 germ cells. To get at these, different reasoning must be used, but the 

 outcome is the same. As a starting point I shall take a contrast em- 

 ployed by the late Dr. John Eyder, of the University of Pennsylvania. 

 He was fond of asking his students whether the hard parts of the body 

 determined the soft parts or whether the reverse is true, thus making the 

 soft parts determine the hard parts. The ordinary assumption is that 

 bony structures are manifestations of the germ cell determinants. This 

 gives the static measurements on which statistics are based, and from 

 which the ordinary view of heredity is derived. Dr. Eyder's view was 

 the opposite of this. He held that the bony structures were the conse- 

 quence of the activity of the soft parts and were laid down later. Those 

 parts became solid and unyielding in which the metabolism was defect- 

 ive. The solid ingredients of the blood were deposited there; bony 

 structures thus came into being and seemed a part of heredity, when in 

 reality they were a consequence and not a cause. 



This view has not won general acceptance. There is, however, 

 enough truth in it to make certain that these are dynamic characters, 

 which must be measured not in terms of structure, but in bodily activity 

 and its effects. An illustration of this is the contrast between anabolism 

 and katabolism, as is also the increased plasticity manifested in the pro- 

 longation of childhood. Plastic brain cells do not result in a single 

 mental trait, but in a change in the whole range of mental activity. 

 The races of slow maturity differ from those rapidly maturing in many 

 traits, and yet they may all be the result of a single variation involving 

 the increased plasticity of brain cells. Among the psychic characters 

 fear is an example of this kind. Cowardice, deceit, falsehood, humility 

 and other traits are clearly the outcome of one fundamental variation. 

 The supplanting of fear by courage would transform a whole civiliza- 

 tion, and modify its best known characteristics. Dynamic variations 

 are thus like environmental modifications. Groups of traits change or 

 appear together, due to one primary cause, innate or external. Types 

 are thus formed that differ in a thousand ways and yet are readily 

 referred back to a few ultimate causes. 



If types are formed in this way, single visible traits can not be 

 altered unless a change is made in other traits that are due to the same 

 cause. The changes from upland to lowland, from cold to hot climate, 

 from damp to dry regions, or from meager to abundant food modifies 

 many external traits at the same time. Paces of men are formed by 

 each external change which continues long enough to compel an adjust- 

 ment to it. Each single visible trait does not have an independent 



