158 INTRODUCTION. 



to your own eyes as my witnesses and judge. For as all true 

 science rests upon those principles which have their origin in 

 the operation of the senses, particular care is to be taken that 

 by repeated dissection the grounds of our present subject be 

 fully established. If we do otherwise, we shall but come to 

 empty and unstable opinions ; solid and true science will escape 

 us altogether : just as commonly happens to those who form 

 their notions of distant countries and cities, or who pretend to 

 get a knowledge of the parts of the human body, from drawings 

 and engravings, which but too frequently present things under 

 false and erroneous points of view. And so it is, that in the 

 present age we have an abundance of writers and pretenders to 

 knowledge, but very few who are really learned and philo- 

 sophers. 



Thus much have I thought good, gentle reader, to present 

 to you, by way of preface, that understanding the nature of the 

 assistance to which I have trusted, and the counsel by which 

 I have been led in publishing these my observations and expe- 

 riments ; and that you yourself in passing over the same ground, 

 may not merely be in a condition to judge between Aristotle 

 and Galen, but, quitting subtleties and fanciful conjectures, 

 embracing nature with your own eyes, that you may discover 

 many things unknown to others, and of great importance. 



Of the same matters, according to Aristotle. 



There is no such thing as innate knowledge, according to 

 Aristotle ; neither opinion, nor art, nor understanding, nor 

 speech, nor reason itself, inhere in us by nature and from our 

 birth; but all of these, as well as the qualities and habitudes, 

 which are believed to be spontaneous, and to lie under the con- 

 trol of our will, are to be regarded as among the number of 

 those things that reach us from without according to nature : 



