Vlll PREFACE. 



would refer such of its readers, as may desire further information upon 

 various topics which are here only slightly touched upon ; and in them, 

 also, will be found references to various original authorities, the intro- 

 duction of which would be .incompatible with the limited scope of a 

 treatise like the present. 



The Author has only to add, that he feels most grateful for the kind 

 appreciation which this Manual has experienced ; and that in the prepa- 

 ration of the present Edition, he has used his best endeavours to render 

 it still more worthy of a favourable reception. The whole treatise has 

 been subjected to a most careful revision ; many statements which the 

 advance of science has shown to be doubtful or erroneous, have been 

 omitted or corrected; and a considerable amount of f new matter has 

 been introduced. Of the First, Eleventh, and Twelfth Chapters, more 

 especially, a considerable proportion has been entirely rewritten ; and 

 the Author ventures to believe that the doctrines which they contain will 

 enable such as may master them to obtain a clearer comprehension 

 of the facts of Physiological Science, than they could previously have 

 acquired. 



REGENT'S PARK, LONDON, 

 September, 1851. 



