CONTENTS. Vll 



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 HYPOTHESIS. 



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 



