100 PHYSIOLOGY OF MUSCLES AND NERVES. 



and this rise can be indicated on a rapidly-mo\'ing 

 myograph plate. If two of these small levers are 

 placed near the ends of a long muscle, and one of the 

 ends is then irritated, the nearer lever is first raised, 

 the more remote not till later. This difference may be 

 read off the plate of the myograph, and thus the 

 speed of the propagation from one lever to the other 

 may be calculated. Aeby, who first tried this experi- 

 ment, found that the speed was from one to two metres 

 in the second, or, in other words, that a contraction 

 excited at one point of a muscle-fibre requires a period 

 of from about ^ot ^^ To~o ^^ ^ second to advance one 

 centimetre. More recent measurements by Bernstein 

 and Hermann show the higher value of from three to four 

 metres in the second. On the death of the muscle, 

 the rate of propagation becomes continually less, finally 

 ceasing entirely in muscles which are just about to pass 

 into a state of death-stiffness, so that on irritation only 

 a slight thickening is seen at the point directly irritated, 

 and this does not propagate itself. Under all circum- 

 stances, however, the excited contraction is confined to 

 the fibres which are themselves actually irritated, the 

 neighbouring fibres remaining perfectly quiescent. In 

 smooth muscle-fibres, however, it is found that the 

 coutractions excited at one point propagate themselves 

 in the adjacent fibres also. The marked distinction 

 which thus appears to exist between smooth and striated 

 muscles would, it is true, disappear if the views of 

 Engelmann, resulting from his study of the urinary 

 duct, are confirmed. According to that writer, the 

 muscular mass of the urinary duct does not consist 

 during life of separate muscle-fibre cells, but forms 

 a homogeneous connected mass which only separates 



