x PREFACE. 
wherever it seemed to me that the passages would 
be sufficiently intelligible to a general reader. 
I may observe, however, that although I have 
throughout kept in view the requirements of a 
general reader, I have also sought to render the 
book of service to the working physiologist, by 
bringing together in one consecutive account all the 
more important observations and results which 
have been yielded by this research. 
G. J. R. 
Lonpon, 1884. 
