COMPENDIUM 



OF 



COMPARATIVE ANATOMY. 



CHAPTER I. 



PRELIMINARY OBSERVATIONS. 



When we turn our attention to the busy theatre of animal life, 

 we are at once attracted by scenes of wonder and delight. The 

 works of nature appear unbounded in extent, variety, and riches. 

 Wherever the eye is cast, from the icy regions of the pole to the 

 scorching sands of the line, it beholds life displayed in forms as 

 endless as they are enchanting. 



Every region and every element is the abode of numerous animals, 

 and is admirably suited to their peculiar living habits and instincts ; 

 the vastness of their number may be estimated from the declaration 

 of the celebrated Ehrenberg, that a single cubic line which is less 

 than a drop of fluid contains 500,000,000 monads. 



But however varied and delightful the occupations of the zoolo- 

 gist may be, his information is still defective, and he perceives that 

 the interior machinery of life is hidden from his observation, and its 

 springs concealed by clouds which nothing but the light of dissec- 

 tions can dispel. 



When once engaged in this captivating department of his inves- 

 tigations, he begins to observe the beautifully progressive develop- 

 ment of organisation, varied and modified in obedience to certain 

 laws ; he will often behold the same animal, according to the parti- 

 cular epoch of its existence, undergoing metamorphosis, appearing 

 under different characters, and playing very different parts on the 

 stage of life. 



Having entered a little more fully into the details of comparative 

 anatomy, he will often observe an organ which has attained a high 

 degree of development, and whose functions are perfectly under- 

 stood in one animal ; diminutive, rudimentary, and apparently use- 

 less in another. Hence it must be obvious, that he who aspires to a 

 perfect knowledge of human structure and function, must extend 

 his researches to an examination of the animal kingdom in general ; 

 and accordingly great advantage will be found in a previous ac- 

 quaintance with some one or more of the most approved classifica- 

 tions in natural history. 



Every classification hitherto proposed has in some particular or 

 other its imperfections ; but it matters little what scale we adopt. 



