in ELECTRICAL EXCITATION OF MUSCLE 229 



innumerable points of the whole area traversed. Experimentally, 

 however, the reaction of such a muscle, constructed of uninuclear 

 cells, in no way corresponds with this theoretical process. We 

 have learned from Engelmann's classical experiments that the 

 ureter, like the heart, conducts itself re both transmission 

 of the excitatory process, and polar excitation by the electrical 

 current, " like a single, gigantic, hollow muscle-fibre." This proves 

 once more that the cement substance does not separate the cells 

 by forming indifferent partition walls, but actually, as it were, 

 brings about the continuity of the substance. A series of 

 muscle-cells, with the ends abutting on each other, and traversed 

 longitudinally by current, would react towards it as a single 

 muscle-fibre, and the connective substance would no more form 

 secondary kathodes and anodes than the transverse discs within 

 the striated fibrils. In the one case, as in the other, there is 

 physiological continuiti/ of substance. This can be proved experi- 

 mentally, both in cardiac, and in various instances of smooth, 

 muscle. If the ventricle, separated from the auricle, of the 

 frog's heart (the " cardiac apex "), is used as the object of experi- 

 ment, the asymmetrical form of the preparation entails the same 

 result as in the sartorius, i.e. the density of current on direct 

 application of the electrodes to either end (apex and base) is very 

 unequal. It is therefore advisable to immerse the apex, accord- 

 ing to Engelmann's method (27, p. 201), in an excitation chamber 

 filled with indifferent fluid, so that there is approximately equal 

 current-density at every point of the preparation, so long as the 

 current is passing. Engelmann employed a glass vessel 13 cm. 

 long, 4 cm. wide, and 3 cm. high, filled to about 1^- cm. with 

 a dilute solution of ISTaCl (0'5 /) and gum arabic (2 /), 

 which the electrodes dipped into. On closing a battery 

 current, or sending in a single induction shock, it is found that 

 if the long axis of the ventricle lies parallel with the lines of 

 current, the cut surface being vertical to the same, ascending 

 currents (i.e. from apex to base) fail to excite immediately, or 

 soon after making the section, or at least excite less effectively 

 than descending currents. After a few minutes, however, the 

 excitability to ascending currents reasserts itself, and rapidly 

 increases, sinking again to zero if the section is freshened. The 

 same dependence of excitation effects on direction of current ap- 

 pears also after injury to one or the other lateral surface of the 



