GENERAL PHYSIOLOGY OF MUSCLE AND NERVE. 123 



contractions, that they give by single contractions; and in this respect they 

 can be said to resemble red striated muscles. The following relations have 

 been found to exist between separate contractions and tetanus in certain muscles : 

 triceps and gastrocnemius of the frog, 1 : 2 or 3 ; the corresponding muscles of 

 the turtle, 1:5; hyoglossus and rectus abdominalis of the frog, 1 : 8 or 9. 1 It 

 is evident that no just estimate of the part played by different groups of muscles 

 in the movement of the body can be reached without a careful analysis of the 

 nature of the contractions peculiar to each of the muscles participating in the 

 movement. 



Both the height and strength of the tetanus is controlled by the intensity 

 of the stimulus. A strong stimulus not only causes the separate contractions 

 of which the tetanus is composed to be higher, but is favorable to the develop- 

 ment of all the other factors which have been described as entering into the pro- 

 duction of tetanus. All normal physiological contractions are supposed to be 

 tetani, and everyone is conscious of the wonderful accuracy with which he can 

 grade the extent and strength of his voluntary movements. The remarkable 

 shading of the intensity of action observable in co-ordinated movements must 

 find its explanation in the adjustment of protoplasmic activity in the nerve- 

 cells of the central nervous system. 



10. Continuous Contractions caused by Continuous Excitation. Attention 

 has been already called to the fact that under certain circumstances a form of 

 continuous contraction may be excited by a continuous constant electric current. 

 If the current be very strong, the short closing contraction may be followed by 

 a more or less continuous contraction the closing (or Wundt's) tetanus, and 

 the short opening contraction may be followed by another continuous contrac- 

 tion, which only gradually passes off the opening (or Hitter's) tetanus. This 

 form of contraction is quite readily excited in normal human muscles, both by 

 direct and indirect excitation. The term " galvanotonus " is sometimes em- 

 ployed for the continuous contraction of human muscles excited by the con- 

 tinuous flow of a constant current. 



The closing tetanus originates at the kathode, and the opening tetanus at 

 the anode. The contraction process may spread rapidly from the point of 

 origin to the rest of the muscle, or, if the muscle be in an abnormal state, or be 

 dying, the contraction may remain localized as a circumscribed swelling, or 

 welt. Although a continuous contraction caused by the constant current is 

 spoken of as tetanus, it is a matter of doubt whether it is a true tetanic condi- 

 tion, for the term tetanus is limited to an apparently continuous contraction 

 resulting from many frequently repeated stimuli. Von Frey 2 expresses the 

 view that the continuous contraction which follows the closing of the contin- 

 uous constant current is a form of tetanus. It is certainly true that the 

 closing tetanus often shows irregular oscillations, suggestive of a more or less 

 intermittent excitation. This might be attributed to irregular chemical changes 

 produced in the muscle-substance by the electricity and leading to irregular 



1 Biedermann : Elektrophysiologie, p. 109. 



2 Archiv fur Anatomic und Physiologic, 1885, p. 55. 



