PECULIARITIES OF MUSCLE TISSUE 69 



cording to Rollett and Engelmann, it amounts to 3-5 m. per second 

 in cold-blooded animals, and to 6 m. per second in warm-blooded 

 animals. For human muscle the value of 10-13 m. in a second has 

 been given. The removal of the muscle from the body, cooling or 

 fatiguing it, and other factors, tend to diminish the speed of this wave. 

 It is independent of the strength of the stimulus. 



Very characteristic progressive contractions of muscle are also 

 exhibited by the stomach, intestine and ureter, but naturally, we are 

 dealing in these cases with smooth muscle which gives the so-called 

 peristaltic wave. This form of contraction is produced by the inter- 

 action of the circular and longitudinal fibers, and although regulated 

 by a nervous mechanism in most cases, this regulation is not absolutely 

 essential, as may be gathered from the observation that the upper por- 

 tion of the ureter contracts with perfect precision although it contains 

 no nervous elements. The same may be said regarding excised seg- 

 ments of arteries. The contraction of the heart is also described as 

 wave-like, the auricles contracting first and the ventricles last, and 

 both in a direction from base to apex. Even excised pieces of cardiac 

 muscle exhibit this wave-like manner of contraction, as may be shown 

 by converting the ventricle of a frog into a zigzag strip by several trans- 

 verse incisions and stimulating this preparation either at its base or 

 at its apex. The contraction will then be seen to progress from the 

 area stimulated to the opposite end of the strip. 



The Muscle Sound. — If a stethoscope is applied over a contracting 

 muscle, such as the biceps, a low rumbling sound is heard, ^ corres- 

 ponding to a frequency of 30-40 vibrations to the second. A sound 

 is also produced by the contracting masseter muscle which may be 

 rendered audible by placing the side of the face flat against a receiving 

 body or by shutting the ears with the index fingers.^ Helmholtz^ has 

 called attention to the fact that this sound corresponds in reality to 

 the resonance sound of the external ear. By determining its pitch with 

 the help of different vibrating reeds held in contact with the con- 

 tracting muscle, he came to the conclusion that it is chiefly constituted 

 by the first overtone of a sound possessing a frequency of vibration 

 of 18-20 in a second. Two very characteristic sounds are also pro- 

 duced by the contracting ventricle of the heart, of which the first is 

 almost entirely muscular. Even excised pieces of ventricle emit a 

 sound. 



1 Discovered by Wollaston and Erman 90 years ago. 



2 Stern, Pfliiger's Archiv, Ixxxii, 1900, 34. 



3 Wissensch. AbhandL, ii, 928. 



