PREFACE. 



THE PRESENT WORK completes the outline of the Organisation 

 of the Animal Kingdom which was begun in that on the Inverte- 

 brates. 1 They may be regarded as parts of a whole, having the 

 same general aim, and, together, form a condensed summary of 

 the subjects of my ( Lectures on Comparative Anatomy and 

 Physiology, according to the Classes of Animals,' delivered in the 

 Theatre of the Royal College of Surgeons of England in the 

 years 1852, 1853, and 1854. 



In the choice of facts, as then and since acquired by science, 

 I have been guided by their authenticity and their applicability 

 to general principles. 



In the first, regard has been had to the agreement of several 

 observers, or to the nature of the fact as making it acceptable on 

 the testimony of a single expert. Appearances that require helps 

 to vision are those that call for multiplied concurring testimony, 

 and on such alone are offered the descriptions and illustrations of 

 the microscopical characters of ( tissues ' premised to most of the 

 chapters. 



In the second aim, the parts and organs, severally the subjects 

 of these chapters, are exemplified by instances selected with a 

 view to guide or help to the power of apprehending the unity 

 which underlies the diversity of animal structures ; to show in 

 these structures the evidence of a predetermining Will, producing 



1 Lectures on the Comparative Anatomy and Physiology of the Invertebrate 

 Animals, 8vo. 1843; 2nd eel. 8vo. 18oo. 



