CARDIAC INHIBITION AND ACCELERATION 319 



certain of its constituents. This phase of disintegration, however, 

 must always be followed by a period during which the material lost 

 is again replenished. In other words, catabolism must be succeeded 

 by anabolism, otherwise the destruction of the living material becomes 

 complete. In accordance with Claude Bernard, the state of inhibition 

 is merely a prolonged period of rest, made necessary by the fact that 

 cardiac muscle, when stimulated, requires an unusually long time for 

 its processes of restitution. Hering and Gaskell have gone one step 

 farther and have suggested that the vagus possesses a true construc- 

 tive function in that it favors the occurrence of metabolic changes. 

 Thus it is held that the excitation of the vagus not only promotes 

 the continuance of that intensity of anabolism which is usual during 

 diastole, but actually augments the processes of breaking down and 

 building up. These data have been made use of by Gaskell 1 in the 

 formation of the so-called trophic theory of inhibition. The conten- 

 tion is that the inhibitor fibers which, as has been shown, are generally 

 included in the vagus nerve, may be looked upon as constituting an 

 anabolic nerve of the heart and must, therefore, be of greatest impor- 

 tance to the nutritive processes going on in this organ. In accordance 

 with this view, the after-effects of their excitation must be very bene- 

 ficial, because a greater formation of contractile material must result 

 therefrom which in turn insures an increased functional capacity of 

 the musculature. In order to strengthen this theory, Gaskell has 

 attempted to prove that these trophic alterations are associated with 

 definite electrical changes. It has been known for a long time that 

 the active part of a tissue is electronegative to its resting part. 

 Quite similarly, it may be assumed, in accordance with the preceding 

 exposition, that the inhibited area of the heart is electropositive to the 

 non-inhibited. In order to prove this point, the auricles of a turtle's 

 heart were rendered inactive by separating them from the sinus 

 venosus. One of the poles of a galvanometer was then connected 

 with the base of the auricles, while the other was permitted to rest 

 upon the apical region which, however, had previously been injured 

 by heat. To begin with, therefore, the aforesaid instrument registered 

 a demarcation-current, the direction of which indicated an electro- 

 negativity at the injured apex. If the auricles were now made to 

 contract, this "current of injury/' immediately gave way to a "current 

 of action. " Moreover, if the vagus nerve was stimulated at this time, a 

 positive variation resulted, indicating the production of an electrical 

 change opposite in potential to that encountered during the contrac- 

 tion of these parts. 



Another theory which is based upon the well-known fact that 

 potassium salts promote the relaxation of the cardiac musculature, 

 has been proposed by Howell and Duke. 2 It is held by these authors 

 that the stoppage of the heart is dependent upon the liberation of 



1 Jour, of Physiol., vii, 1886, 451. 



2 Am. Jour, of Physiol., xxi, 1908. 



