ANIMAL MECHANICS 



INTRODUCTION 



To prepare us for perceiving design in the 

 various internal structures of an animal body, we 

 must, first of all, know that perfect security 

 against accidents is not consistent with the scheme 

 of nature. A liability to pain and injury only 

 proves how entirely the human body is formed 

 with reference to the mind; since, without the 

 continued call to exertion, which danger and the 

 uncertainty of life infer, the development of our 

 faculties would be imperfect, and the mind would 

 remain, as it were, uneducated. 



The contrivances (as we should say of things 

 of art) for protecting the vital organs are not 

 absolute securities against accidents ; but they 

 afford protection in that exact measure or degree 

 calculated to resist the shocks and pressure to 

 which we are exposed in the common circumstances 

 of life. A man can walk, run, leap, and swim, be- 

 cause the texture of his frame, the strength and 

 power of his limbs, and the specific gravity of his 

 body are in relation with all around him. But, 



