450 Opposable Power of the Thumb 



never occurred to me before ; and I was aware, moreover, 

 that no zoologist, with whose works I was acquainted, had 

 recorded a similar fact. Baron Cuvier, indeed, had previously 

 separated the Ouistitis (Hapale) from the other American Simi- 

 adae, partly on this account ; but, in so doing, he had expressly 

 recognised the rest of these mammals as true Quadriimana, 

 in the strict and legitimate sense of the term, and actually 

 included them in the same group with the common Simiae of 

 Asia and Africa, a group of which the zoological character 

 depended entirely upon this circumstance of the thumb being 

 opposable on the anterior as well as on the posterior ex- 

 tremities. In this respect Baron Cuvier was only following 

 the example which had been set him by Ray and Linnaeus ; 

 nor did contemporary zoologists dissent from his opinion upon 

 this point. 



I was, consequently, aware that the observation which I 

 had made with regard to these two Mycetes had not been 

 previously recorded by systematic writers ; I therefore resolved 

 to prosecute the enquiry, by extending my examination to 

 other genera and species of American Simiadae : but such is 

 our natural veneration for authority, that I confess it was not 

 without very great caution and frequent misgivings, that I 

 persevered in an enquiry where I found my own observations, 

 at every step, directly opposed to the express declaration of 

 the most illustrious masters of zoological science. It required 

 a considerable time, indeed, to familiarise my mind with the 

 new ideas and new views which these observations suggested ; 

 to persuade myself, in short, that the American Simiadae were 

 not Quadrumana : in fact, so strongly was I impressed with 

 the weight of authority, that it was actually some time before 

 I could give its due weight to the evidence of my own senses. 

 This state of mind, whilst it did not deter me from pursuing 

 my observations, armed me with additional caution ; and, 

 though the authority of Nature soon asserted her preeminence 

 over that of system, I guarded scrupulously against admitting, 

 as conclusive evidence, such facts as rested only on the 

 examination of preserved specimens, and resolved to wait 

 patiently till I should have an opportunity of examining at 

 least one species of each genus in the living state, where the 

 observation of the organ in action, and in connexion with its 

 proper function, would remove all possibility of deception. 



During the last six years, I have been engaged in pro- 

 secuting this interesting enquiry, from time to time, whenever 

 an occasion presented itself; and, as I have, during this 

 period, enjoyed frequent opportunities of examining many 

 different species of American Simiadae, including examples 



