iv ELECTROMOTIVE ACTION IN MUSCLE 343 



for the moment we can only say that the muscles of the frog's 

 thigh, e.g. sartorius, may be obtained perfectly free from current 

 without much difficulty (16). The proof that skeletal muscle 

 can always be obtained free of current with proper precautions 

 does not, however, exhaust the evidence against electromotive 

 action in uninjured muscle. In 1874 Engelmann (12) pointedr 

 out that the heart is a muscle peculiarly well adapted to in- 

 vestigation in the normal, uninjured condition. Experimentally, 

 indeed, with every variety of lead-off, it gives no current. It 

 is, however, obvious that an artificial section of the heart must 

 be as negative as that of any other muscle ; and it was with 

 knowledge of this that Matteucci constructed a battery of pigeons' 

 hearts with transverse sections. It is interesting relatively to 

 the theory of the longitudinal sectional current that (Engelmann, 

 12) the E.M.F. between the artificial transverse section and 

 natural surface of cardiac muscle declines very rapidly. This is 

 the more striking since it has long been known (as pointed out 

 by du Bois) that the longitudinal current of monomerous skeletal 

 muscle, when once developed, is singularly constant. Engelmann 

 found, e.g., that the E.M.F. in the sartorius in 1 hour fell to 

 81-1 %, in 24 hours to 43'6 %, and in 48 hours to 30'8 % 

 (average of 45 experiments). Kenewing the section, i.e. application 

 of a fresh, deeper cross-section, is usually of little use, leading at 

 most to a slight augmentation of the muscle current. In the 

 heart the results are very different. Here refreshing the old 

 section is sufficient to restore the E.M.F. to its original vigour. 

 Hence it might appear as though the development of the parelec- 

 tronomic layer could be directly observed in this case. The fact, 

 however, is easily interpreted, considering the analogous behaviour 

 of polymer ous skeletal muscle. Two long muscles, divided into many 

 short segments by tendinous intersections, run along the inner side 

 of the body-wall of Salamandra maculata. If such a band-shaped 

 muscle is excised, divided transversely through a single segment, 

 and protected from drying, it will be found infallibly that after 

 some time this injured segment alone shows symptoms of rigor, 

 while the rest retain their normal appearance and excitability, 

 i.e. mortification has been arrested at the nearest tendinous inter- 

 section. On leading off from such a muscle to the galvanometer, 

 on the one side from an artificial cross-section, on the other from 

 any point of the muscle surface, a normal current will of course 



