298 



MUSCULAR CONTRACTION. 



LECT. XVI. 



result of the numerous observations of Fodera, Edwards, 

 Weber, &c. 



Experiment shows that the volume of a muscle does 

 not sensibly alter during contraction. This vessel contains 

 a torpedo and a prepared frog ; it is filled with water, and 

 closed with a cork perforated by a narrow tube, in which 

 the liquid rises. Two insulated, varnished wires pene- 

 trate the vessel, and when brought into communication 



Fig. 21. 



Fragments of Striped Elementary Fibres, showing a cleavage in opposite direc- 

 tions; magnified 300 diameters; 1, longitudinal cleavage; the longitudinal and trans- 

 verse lines are both seen ; some longitudinal lines are darker and wider than the 

 rest, and are not continuous from end to end ; this results from partial separation of 

 the fibril!,'!'; 6, fibrilhc, separated from one another by violence at the broken end of 

 the fibre, and marked by transverse lines equal in width to those on the fibre; 7, 8 

 represent two appearances commonly presented by the separated single fibrillae, (more 

 highly magnified ;) at 7 the borders and transverse lines are all perfectly rectilinear, 

 and the included spaces perfectly rectangular; at 8 the borders are scalloped, the 

 spaces bead -like; when most distinct and definite, the fibrilla presents the former of 

 these appearances ; 2, transverse cleavage ; the longitudinal lines are scarcely visi- 

 ble ; 3, incomplete fracture following the opposite surfaces of a disc, which stretches 

 across the interval and retains the two fragments in connexion ; the edge and surface 

 of this disc are seen to be minutely granular, the granules correspond in size to the 

 thickness of the disc, and to the distance between the faint longitudinal lines; 4, an- 

 other disc nearly detached ; 5, detached disc more highly magnified, showing the sar- 

 cous elements. 



with the poles of a pile, excite contractions both in the 

 torpedo and frog ; but you perceive that no change has 



