250 ELECTRO-PHYSIOLOGY CHAP. 



direct excitability. Fredericq (1) observed a negative variation 

 in the nerves of rabbit, dog, and horse, with electrical stimulation, 

 up to 24 hours after death, and. Boruttau (20) claims to have 

 kept frogs' nerves for 7 to 12 days at low temperature without 

 impairing their faculty of giving a distinct, though weak, negative 

 variation when electrically excited. Lastly, Steinach (21) has 

 observations to the effect that (recently) dried frogs' nerves 

 yield a genuine negative variation again, if they are bathed in 

 0'6 % NaCl. Starting from certain purely physical effects on 

 the so-called core-model (infra), Boruttau thence concludes that 

 " the persistence of those properties in the nerve, by virtue of 

 which its galvanic manifestations when at rest (demarcation 

 current), and during electrical action (negative variation), are to 

 be observed, must be. referred less to the survival of that by 

 which the nerve is still capable of discharging muscular activity, 

 than to the conservation of its normal structure." In other 

 words, " the galvanic effect known as the negative variation of 

 current appears in the nerves of dead preparations also, when 

 these are submitted to the same electrical stimulus that calls out 

 muscular activity in fresh preparations." " Both mechanical 

 stimuli (cutting, crushing) and chemical excitation " produce, 

 according to Boruttau, a negative variation from " dead " frogs' 

 nerves, 8 days old, on the capillary electrometer, and he finds 

 the same result from the vago-sympathetic of the dog, on 

 tetanising it mechanically 2 to 3 days after excision. 



Granting the facts as stated in these observations, the con- 

 clusions can hardly be accepted. Unless absolute reason can be 

 shown to the contrary, we are presumably justified under all 

 circumstances in maintaining that the negative variation in nerve, 

 as in muscle, is the galvanic expression of excitation in living nerve 

 a vital physiological manifestation and not merely an " undu- 

 lating (physical) katelectrotonus." No one accustomed to consider 

 the excitatory manifestations of living matter from a general point 

 of view can for an instant doubt that the negative variation is 

 to be regarded as a special case of the action current, not merely 

 iii medullated, but also in non-medullated nerve, in smooth and 

 in striated muscle ; probably indeed in many other kinds of 

 excitable protoplasm as the concomitant, and effect, of those 

 chemical alterations which, properly speaking, constitute the pro- 

 cess of excitation. Clearly we ought not to revive in " nerve 



