Aim and Method of Comparative 

 Anatomy 



10 



Comparative anatomic description is of little interest and of no 

 scientific value unless it can be made to yield meaning. Facts of verte- 

 brate comparative anatomy played an especially important part in the 

 beginnings of the Theory of Evolution. Much of the strongest evidence 

 which led to general scientific acceptance of the theory was derived 

 from vertebrate anatomy and embryology. The theory has great human 

 significance. Aside from the practical importance of vertebrate anat- 

 omy in relation to Medicine, its primary scientific importance is in its 

 bearing on the problems of Evolution. 



Since the time of Lamarck, therefore, the dominant purpose of 

 Comparative Anatomy, always allied with Comparative Embryology 

 and Paleontology, has been the obtaining of such knowledge as will 

 either establish Evolution as a fact or else compel discarding the 

 theory. In so far as the evidence justifies acceptance of the theory, the 

 further business of Comparative Anatomy is to work out the complete 

 evolutionary history and relationships of animals — and Man is a back- 

 boned animal. In going about this latter business, how shall Compara- 

 tive Anatomy proceed? 



The method of the science is implied in the name Comparative 

 Anatomy. The principle is very simple. Animals are judged to be 

 closely related or more or less distantly related according to whether 

 they are anatomically closely similar or more or less unlike. In practice, 

 it is far from simple. It is difficult to find accurate measures of anatomic 

 difference. Also it often happens that two animals may be closely 

 similar in nearly all respects, but very unlike in one or two points, or 

 else mainly different and yet, in some conspicuous way, alike. Further, 

 in the mere process of comparing, various perplexities are encountered. 



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