PREFACE TO THE SECOND EDITION. 



THE object of the writer of the present work has been twofold : 

 first, to lay before the Naturalist a complete view of the organi- 

 zation and physiological relations of every class of living beings ; 

 and secondly, to offer to the Anatomical Student a succinct 

 account of the structure and development of the vital organs 

 through all the modifications they present in the long series of 

 the animal creation. 



Such were the intentions of the Author, as announced at the 

 commencement of his undertaking ; and the reception the first 

 edition received at the hands of the public has been such as to 

 afford gratifying proof that his efforts to facilitate the progress of 

 the cultivators of a science the importance of which is becoming 

 every day more conspicuous have not been unsuccessful. 



Since the publication of the preceding edition, however, great 

 and important advances have been made in our knowledge : many 

 and earnest have been the labourers in this enticing field, and 

 proportionately encouraging have been the results. The inde- 

 fatigable industry of Professor Owen, conspicuous in every de- 

 partment of our science, has, by his invaluable analysis of the 

 vertebrate skeleton, not only re-modelled the nomenclature of the 

 osteologist, but placed in the hands of the Geological Student a 

 light wherewith to guide his steps amid the darkness of departed 

 worlds. The improvements in our microscopes, and the zeal of 

 our microscopists, have much advanced our knowledge of the In- 

 fusorial organisms. The researches of Van Beneden and Siebold 

 relative to the embryogeny of parasitic worms open before us a 

 new field of research; while the observations of Steenstrup, 



