396 ELECTRO-PHYSIOLOGY CHAP. 



which can be used is unfortunately limited, chiefly because a 

 locally discharged excitation remains localised in most smooth 

 muscular organs, and is not propagated further. Cardiac muscle, 

 on the other hand, the physiological properties of which entitle it 

 to some extent to a middle place between striated muscle and 

 smooth muscle -cells, presents an object peculiarly appropriate 

 to the investigation of galvanic phenomena. As early as 1855 

 Ko'lliker and H. Miiller (31) observed the negative variation on 

 spontaneous contraction of a frog's heart provided with an 

 artificial cross -section, by means of the multiplier; they soon 

 discovered that secondary contraction may also be obtained 

 from the same preparation, if the nerve of a rheoscopic limb is 

 properly bridged across the longitudinal and transverse sections. 

 Each systole is followed by a twitch in the leg, occurring after 

 the auricular ; and almost imperceptibly before the ventricular, 

 systole. " The twitch took effect sometimes in the lower part of 

 the leg, sometimes at the tarsus and toes, and was visible through- 

 out as a single transitory contraction" (I.e. p. 99). 



It was presently found that the same experiment produced 

 results in the intact heart also, even when the secondary nerve 

 was laid transversely across the middle of the anterior surface of 

 the ventricle. The surface of the uninjured heart being iso- 

 electric (as was shown above), this last observation on currentless 

 cardiac muscle shows once more that the interpretation of 

 secondary contraction as a consequence of negative variation, as 

 given by du Bois, is not justified, but that the electromotive effects 

 (current of action) associated with the activity of the muscle 

 must have acted as a discharging stimulus to the nerve lying 

 upon it. The facts discovered by Ivolliker and Miiller were 

 subsequently confirmed and extended by Meissner and Cohn 

 (32). Donders (33) repeated the experiment on secondary 

 excitation from the heart with the aid of the graphic method. 

 He recorded simultaneously in dog and rabbit the heart-beats 

 and the contractions of a frog's leg, the nerve of which rested on 

 the heart. As a rule each systole discharged a simple twitch in 

 the leg. Donders found, like Kolliker and Miiller before him, 

 that the simple systole was invariably followed by a secondary 

 double contraction. It was always possible to demonstrate that 

 the secondary twitcli <//>/i<'/< /'<<! m/7/Y/ 1 than the primar// ]i/'/i con- 

 traction (about y 1 ^ sec. in rabbit). In a recently killed dog, whose 



