Circulation of the Blood 159 



observations based on the evidence of sense, or to 

 oppose the experiments adduced, by other experiments 

 of the same character ; nay, no one has yet attempted 

 an opposition on the ground of ocular testimony. 



There have not been wanting many who, inex- 

 perienced and ignorant of anatomy, and making no 

 appeal to the senses in their opposition, have, on the 

 contrary, met it with empty assertions, and mere 

 suppositions, with assertions derived from the lessons 

 of teachers and captious cavillings ; many, too, have 

 vainly sought refuge in words, and these not always 

 very nicely chosen, but reproachful and contumelious ; 

 which, however, have no farther effect than to expose 

 their utterer's vanity and weakness, and ill breeding 

 and lack of the arguments that are to be sought in 

 the conclusions of the senses, and false sophistical 

 reasonings that seem utterly opposed to sense. Even 

 as the waves of the Sicilian sea, excited by the blast, 

 dash against the rocks around Charybdis, and then 

 hiss and foam, and are tossed hither and thither ; so 

 do they who reason against the evidence of their 

 senses. 



Were nothing to be acknowledged by the senses 

 without evidence derived from reason, or occasionally 

 even contrary to the previously received conclusions of 

 reason, there would now be no problem left for dis- 

 cussion. Had we not our most perfect assurances by 

 the senses, and were not their perceptions confirmed 

 by reasoning, in the same way as geometricians proceed 

 with their figures, w r e should admit no science of any 

 kind ; for it is the business of geometry, from things 

 sensible, to make rational demonstration of things that 

 are not sensible ; to render credible or certain things 

 abstruse and beyond sense from things more manifest 

 and better known. Aristotle counsels us better when, 

 in treating of the generation of bees, he says : l " Faith 

 is to be given to reason, if the matters demonstrated 



1 De General. Animal, lib. iii, cap. x. 



