120 ELECTRO-PHYSIOLOGY CHAP. 



of closure and opening tetanus to throw a second nerve-muscle 

 preparation into secondary tetanus, as discussed in vol. i., has 

 obviously no application as a counter-argument). Inasmuch as 

 cardiac muscle and the ureter exhibit a similar reaction, this 

 would seem to be a general law, applicable to all excitable 

 substances. The time -distribution, i.e. succession of single 

 excitatory impulses, differs of course in different cases, and 

 exhibits a regular gradation. As a rule, therefore, and contrary 

 to du Bois-Eeymond's " universal law of excitation," it must be 

 affirmed that the electrical current flowing at constant density 

 gives rise (locally, at least) to continuous excitation, and the 

 problem is rather why such excitation is not invariably trans- 

 mitted ; or, if transmitted, is not uninterruptedly expressed at 

 the peripheral organ. The nature of the terminal organs is here 

 undoubtedly of the first importance, as appears plainly from the 

 afferent nerves. 



The earlier electricians knew that centripetal impulses excited 

 by the action of a constant current produce, in addition to a 

 sharp make and break twinge, constant sensations, which may 

 become insupportable with sufficient strength of current. It is 

 true that the peripheral, sensible end-organs are nearly always 

 coexcited, while there have only been solitary experiments upon 

 the continuous excitation of sensory nerve-trunks by the direct 

 action of the constant current. The fact (already known to Volta) 

 of an excentric irradiation of pain so long as the electrodes are 

 applied below the joint of the elbow, comes under this category. 

 Griitzner (6) further showed that both ascending and descending 

 currents were effective throughout their passage, when the central 

 end of the dog's sciatic was excited after previous curarisation, 

 and division of the vagus on one side. A considerable rise of 

 blood-pressure occurred at and during closure, with a simultaneous 

 acceleration of pulse, which changed after opening the circuit, or 

 at the end of excitation, into its contrary, i.e. slowing down of 

 the pulse. Griitzner found the same results on stimulating the 

 central end of the vagus, with additional respiratory modifications, 

 consisting in arrest of the diaphragm in expiration, or retarded 

 respiration with expiratory pauses. The same observations have 

 recently been confirmed and extended by Langendorff and E. 

 Oldag (7). By gradually shunting the current into the nerve, 

 they were enabled to observe its continuous action, and obtained, 



