X PREFACE TO THE FIRST EDITION. 



illustrations are indispensable for the proper understanding of the 

 printed descriptions ; the latter being often necessarily somewhat 

 intricate, and requiring absolutely the assistance of properly 

 arranged figures and diagrams. Of the two hundred and fifty- 

 four illustrations in the present volume, only eleven have been 

 borrowed from other writers, to whom they will be found duly 

 credited in the list of woodcuts. 



Of the remaining illustrations, prepared expressly for the pre- 

 sent work, the drawings of anatomical structures, crystals, and 

 microscopic views generally were all taken from nature. The 

 diagrams were arranged, for purposes of convenience, in such 

 a manner as to illustrate known anatomical or physiological ap- 

 pearances, in the most compact and intelligible form. 



Physiological questions which are in an altogether unsettled 

 state, as well as purely hypothetical topics have been purposely 

 avoided, as not coming within the plan of this work, nor as calcu- 

 lated to increase its usefulness. 



XEW YORK, January 1, 1859. 



