Xli PREFACE. 



ture and extent of these changes. It will be proper, 

 therefore, in the reader to abstract as much as possi- 

 ble from any preconceived opinions on these sub- 

 jects ; and to consider, that it is only by a scrupu- 

 lous examination of the facts adduced, and of the le- 

 gitimacy of the conclusions drawn from them, that the 

 views of the author can be finally established pr over- 

 thrown. To try the merits of these views, not by 

 the evidence on which they rest, but by anticipating 

 difficulties which they may be supposed hereafter to 

 create, would be an open departure from the only 

 mode in which we can ever hope faithfully to inter- 

 pret the laws of nature. 



Whatever may be the ultimate judgment passed 

 upon the general merits of his performance, the au- 

 thor indulges the hope, that some advantage at least 

 may indirectly result from it. The extensive series 

 of facts which he has brought together, and the 

 analogies which, from the evidence of experi- 

 ment, he has endeavoured to trace anjong them, 

 may direct the attention of future inquirers to a 

 more comprehensive view of the subject than has 

 yet been taken, and impart a new degree of inte- 

 rest and utility to the research. The attempt also 

 to combine, in every instance, the demonstrations of 

 anatomy with the chemical phenomena which we ob- 

 serve, and to Consider both in connection and sub- 



