CHAPTEE XYI. 



MTJSCULAK COISTTEACTION. PASSIVE OKGANS OF LOCOMOTION. 



Changes in the form of the muscular fibres during contraction Secousse, 

 Zuckung, or spasm Spasm produced by artificial excitation Mechanism 

 of prolonged muscular contraction Tetanus Electric phenomena in the 

 muscles Muscular effort Passive organs of locomotion Physiological 

 anatomy of the bones Fundamental substance Haversian rods Haver- 

 sian canals Lacunse Canaliculi Bone-cells, or corpuscles Marrow of 

 the bones Medullocells Myeloplaxes Periosteum Physiological anat- 

 omy of cartilage Cartilage-cavities Cartilage-cells Fibro-cartilage. 



THE stimulus of the will, conveyed through the conduct- 

 ors of motor influences from the brain to a muscle or set of 

 muscles, produces an impression upon the muscular fibres and 

 causes them to contract. In parts where the muscles have 

 been exercised and educated, this action is regulated with ex- 

 quisite nicety, so that the most delicate, rapid, as well as 

 powerful contractions may be produced. Certain movements, 

 not under the control of the will, are produced as the result of 

 unconscious reflection from a nervous centre, along the motor 

 conductors, of an impression made upon sensitive nerves. 

 During this action, certain important phenomena are ob- 

 served in the muscles themselves. They change in form, 

 consistence, and, to a certain extent, in their constitution ; 

 the different periods of their stimulation, contraction, and re- 

 laxation are positive and well-marked ; their nutrition is for 

 the time modified ; they develop galvanic currents ; and, in 

 short, present a number of general phenomena, distinct from 

 the results of their action, that are more or less interesting 

 and important to the physiologist. 



