478 CONCLUSION 



of ever-increasing importance ; the direct influence of the en- 

 vironment also assumes a greater importance than among species 

 in a state of nature, though it remains relatively insignificant 

 compared with changes in tradition and changes in the germinal 

 constitution. Germinal change, however, retains almost its full 

 importance so far as permanent changes in physical characters 

 are concerned. 



We have seen that physical characters as presented to us are 

 the expression of the inter-action between certain germinal 

 predispositions and a certain environment, and that, disease 

 apart, such variations as usually occur in the environment do 

 not in any notable manner affect these characters. Tradition 

 does not enter directly into the expression of physical character ; 

 it alters the environment, it is true, but that is another matter. 

 Nevertheless when we come to investigate the smaller differences, 

 such as those which are found as between members of different 

 classes in a modern community, the greatest caution is necessary 

 before the differences in the environment are ruled out as con- 

 tributory factors in producing these differences. Broadly speaking, 

 we may say that differences in stature, eye colour, eyesight, 

 muscular power, and so on, are all, though in varying degrees, 

 because different organs vary in their susceptibility to environ- 

 mental differences, expressions of germinal differences. It follows 

 that, so far at least as physical characters are concerned, the 

 germinal constitution is of primary importance. Disease due to 

 parasites is a question apart. The parasites might be eliminated, 

 ^or conceivably preventive medicine might render susceptibility 

 to disease of little account. Disease due to structural defects 

 must be classed with other physical characters and, whether it 

 be that we are considering health (immunity from parasitic 

 disease except ed), stature, eye colour, or any other physical 

 character, it is to the germinal constitution that we must look 

 as the factor of chief importance. 



It is not, however, of changes in physical characters but of 

 changes in mental characters of which we think when we ask 

 what it is that has caused those events the recording of which is 

 the province of historians. There are three factors to be con- 

 sidered, germinal change, traditional change, and the direct effect 

 of the environment, which latter factor we may pass over, merely 

 recalling that it can at times as in the case of chronic disease 



