210 PREFACE. 



these experiments with the attention and circumspection neces- 

 sary upon so curious a subject, requires more time than my 

 other employments would permit, on which account I have 

 been obliged to defer the publication of them till this time, 

 when I hope their greater accuracy will in some measure com- 

 pensate for my delay. 



I have chosen to publish them under the form of chapters 

 and sections, for the sake of more precision for those who are 

 not much conversant in anatomy; at the same time I natter 

 myself this method will not be wholly unacceptable to those 

 who have made that branch of natural philosophy their parti- 

 cular study : for as the facts are numerous, by this method 

 they will be referred to with much greater facility, and the 

 propriety of the inferences will be judged of the more readily. 



To such gentlemen as are not well acquainted with ana- 

 tomy, the subject, from the quantity of new matter it contains, 

 may appear obscure ; but as this is a doctrine in which not 

 only the medical part of the world, but philosophers in general, 

 are much interested, we most earnestly entreat them to sus- 

 pend their judgment till they have deliberately considered all 

 the facts. The inductions will then, I presume, be thought just. 



As it is the ultimate end of philosophy to investigate truth, 

 so it must afford the greatest pleasure to generous minds to 

 embrace it, in whatsoever form they find it. The remarks 

 and criticisms of such I shall esteem the greatest obligations. 

 Some there may be who, having early imbibed prejudices, will 

 find it very difficult to shake them off; others may be very 

 unwilling to believe that they have erred both in opinion and 

 practice all the preceding part of their lives. I shall at all 

 times esteem it a happiness and an honour to remove the 

 doubts of these gentlemen, not so much from a wish to per- 

 suade by argument, as to convince by demonstration. 



And as many gentlemen who are not possessed of glasses 

 may be desirous of seeing the experiments upon the blood, I 

 shall at all times be happy in showing them to such gentlemen 

 as will do me the favour of calling upon me. 





