18 THE MAMMALIA [SECT. A 



of the genital organs, Man differs more widely from Woman 

 than from an individual of his own sex in such a comparatively 

 lowly form as a shrew-mouse. It follows therefore that inferences 

 from observations on various systems and organs must be introduced 

 into what may be called the morphological balance sheet, due 

 allowance being made for conditions determined by sex and by age. 



The foregoing remarks will serve to indicate the importance of 

 taking into consideration the evidence given by several systems 

 and of summing up the results thus obtained. 



In so doing, attention is directed to the relative value of the 

 different pieces of evidence. To illustrate this side of the ques- 

 tion, the simple example already adduced, of the Fish and the 

 Whale, may be employed again. Thus in this instance, the evi- 

 dence of the respiratory organs admittedly overrides that provided 

 by the external form and proportions. Such ratings or assessments 

 are to some extent matters of convention and agreement. Organs 

 which are less exposed to external influences are held usually to 

 be the surest guides. But while it is generally safe to rely more 

 implicitly on the form of the brain or heart, for instance, than on 

 the external characters, yet each case must be decided upon con- 

 siderations peculiar to its circumstances. These again bring in 

 physiological principles which cannot be divorced from those of 

 Morphology. 



We may now note, although this is an anticipation, that when 

 the criterion of structure is employed, the determination of the 

 position and relations of Man in the Class Mammalia is more easy 

 than when other criteria are made use of. On this subject the 

 verdict of Morphology is clear and unhesitating. 



It is further to be noted that the most primitive morpho- 

 logical type of mammal is as a rule, though not always, the 

 most simple; and the less primitive is often, though by no means 

 always, the more complex in construction. 



The comparative method of study is applicable to all the 

 mammalian forms, and when the test of Morphology is applied to 

 Man himself it will be found as has been said that his relative 

 position is well defined. This application of the principles of 

 Morphology to the special case of Man constitutes the essence 

 of Physical Anthropology. 



