296 MUSCULAR CONTRACTION. LECT. XVI. 



LECTURE XVI. 



MUSCULAR CONTRACTION. ANIMAL MECHANICS. 



ARGUMENT. Muscular contraction : agents which affect it ; influence of 

 the nervous force, velocity with which it is propagated. Analogy be- 

 tween the structure of muscular fibres and of the electric organs of 

 fishes. Phenomena of muscular contraction. Schvvann's observations 

 on the degrees of muscular force evinced during contraction. Hypo- 

 thesis of muscular contraction. 



Locomotion of animals. The locomotive organs may, in general, be re- 

 duced to a system of levers. Discovery of the brothers, Weber, that the 

 lower limbs oscillate during progression. Influence of atmospheric 

 pressure on the coxo-femoral articulation. 



Passive organs of locomotion : composition and structure of bone. Rela- 

 tion of the length and thickness of bones to their resisting power. 



Muscular power. Velocity and extent of motion, how gained. Borelli's 

 principles for estimating the force of muscles. The fore arm is a lever 

 of the third kind. Standing on one foot is effected by a lever of the 

 second kind. Estimated strength of the muscles of the fore arm. 



The essential part of the mechanism of locomotion is either elongation or 

 shortening. 



IN the preceding lecture we were engaged in giving an 

 exposition of the laws of the nervous force, and in investi- 

 gating the causes of its development ; as far, at least, as is 

 allowable in a course of lectures, from which vague notions, 

 and purely hypothetical deductions, have been carefully 

 excluded. 



Muscular contraction and its result, locomotion, are the 

 effects of the force which we have now to study ; and in 

 treating of these subjects, we shall confine ourselves to that 

 which is more positive, and best established. 



