CONTENTS. 



vii 



PAGE 



form of work, but do not increase its quality — Necessity of 

 alternate movements in living motive powers — Dynamical energy 

 of animated motors 59 



CHAPTER VIII. 



HARMONY BETWEEN THE ORGAN AND THE FUNCTION.— 

 DEVELOPMENT HYrOTHESIS. 



Each muscle of the body presents, in its form, a perfect harmony 

 with the nature of the acts which it has to perform — A similar 

 muscle, in different species of animals, presents differences of 

 form, if the function which it has to fulfil in these different 

 species is not the same — Variety of pectoral muscles in birds, 

 according to their manner of flight— Variety of muscles of the 

 thigh in mammals, according to their mode of locomotion — 

 "Was this harmony pre-established ?— Development hypothesis — 

 Lamarck and Darwin 69 



CHAPTER IX. 



VARIABILITY OF THE SKELETON. 



Reasons which have caused the skeleton to be considered the least 

 variable part of the organism — Proofs of the yielding nature of 

 the skeleton during life, under the influence of the slightest pres- 

 sure, when long continued — Origin of the depressions and pro- 

 jections which are observed in the skeleton — Origin of the 

 articular surfaces — Function rules the organ — Variability of the 

 ^muscular system 85 



BOOK THE SECOND. 



FUNCTIONS: TERRESTRIAL LOCOMOTION. 



CHAPTER I. 



OF LOCOMOTION IN GENERAL. 



Conditions common to all kinds of locomotion — Borelli's comparison 

 — Hypothesis of the reaction of the ground — Classification of the 

 modes of locomotion, according to the nature of the point of 

 resistance, in terrestrial, aquatic, and aerial locomotion — Of the 



