

18U.] 157 [Wilder. 



I. HISTORICAL SKETCH. 



I have ventured to represent the progress of the question of Inter- 

 membral Homologies since 1774, by the foregoing diagram. The 

 brace at the left includes a reference to the general comparisons be- 

 tween armus, 1 (anterior limb), and skelos (posterior limb), which were 

 made by the ancient anatomists and by their successors prior to 1 7 74. 

 Between these and the recent general comparisons, and forming a 

 common point of convergence of the one, of divergence for the other, 

 is the ' ' detailed comparison " of Vicq d'Azyr. 



It is not easy to do justice to this great anatomist's paper upon the 

 membra, partly because it contains no figures, but chiefly because his 

 words are capable of three different interpretations, which have 

 served as the basis for as many distinct views of intermembral homol- 

 ogies. 



Vicq d' Azyr seems to have had in his mind three ideas : — 



1. That armus and skelos really correspond, not only as 

 membra, but in detail. 



2. That similar parts face in opposite directions. 



3. That, therefore, in order to make a comparison more readily, 

 it is convenient to place the armus of one side, reversed, against the 

 skelos of the other side. 



In brief, he wished to demonstrate a certain proposition; in so 

 doing he recognized a certain fact, and therefore followed a certain 

 method. His successors have all admitted the truth of the proposition, 

 and the majority have gone no farther than to recognize the general 

 correspondence between the several segments and articulations of the 

 membra. 



But those who have noted the admission by Vicq d' Azyr of an 

 antagonism between these corresponding parts, whether or not they 

 saw the importance of the principle of symmetry, have more or less 

 distinctly recognized the fact, and have, therefore, followed his method 

 of comparison as a method, and nothing more. This is evident from 

 the words of Turenne, 21,. Pagenstecher, 54, and Haughton, 62; and 

 some, if not all of those who have been much criticized and even ridi- 

 culed (by Owen, 20, 335; Martins, 37; Wilder, 52; Wyman, 55) for 

 the extraordinary methods adopted in making their comparisons, 

 ought rather to be included among those who have followed Oken, in 

 recognizing more or less distinctly the importance of this symmetrical 

 antagonism as a law of organization. 



1 The nomenclature of parts will be discussed hereafter. 



