254 PHYSIOLOGY. 



quently, the first ligature cutting off the motor power of Kemak's, the 

 auricle and ventricle stand quiescent, while after the second ligature, 

 cutting off also the inhibition of von Bezold's ganglia, the ventricle, 

 actuated by Bidder's ganglia alone and unopposed, again commences 

 to beat. 



Dogiel and Archangelsky, in a frog's heart, have extirpated the 

 ganglia of Bidder, the intraventricular ganglia, and the ganglion cells 

 and nerves which lie about the auriculo-ventricular groove, and found 

 that the ventricle lost the power to rhythmically contract, although its 

 muscle and nerves were retained up to the ganglion cells, which had 

 been removed. In such a heart, robbed of its ganglion cells, the law 

 of Bowditch, that a minimal irritation is at the same time a maximal 

 one, fails, for the cardiac muscle gave varying heights of contraction 

 with varying strength of the electrical current. 



Marie Imchanitzky, working in Kronecker's laboratory, found in a 

 lizard, where neither muscle-bridges connected the auricle to the 

 ventricle, nor any bundle of muscle-fibers in the septum corresponding 

 to that of His, that ligation of the nervous cords which are the only 

 connection between the auricles and ventricles, made the auricles beat 

 10 per minute and the ventricles 3, then it was 14 to 6. Besides 

 these nervous cords, only connective tissue can be noticed between the 

 auricles and ventricles. Here there is a purely neurogenic origin of 

 co-ordination of the heart-beat. 



Carlson has made numerous experiments upon the crab's heart, 

 which prove the neurogenic theory of its heart action. The neuro- 

 genic theory has received some support fey experiments upon the heart 

 of warm-blooded animals. 



Kronecker and Schmey found that a needle thrust into the heart 

 at the lower border of the upper third of the septum produced fibrillary 

 contractions, which Kronecker believed was due to a puncture of the 

 co-ordinating nerve center situated at that point, or to his later theory 

 that the needle irritates a vasomotor center which produces a deficient 

 blood-supply to the ventricle. 



Myogenic Theory. This theory is the one generally held by the 

 majority of physiologists. The nerveless apex of a frogfs heart has 

 been kept twenty-one days and it was still able to contract upon stimu- 

 lation. In such a preparation all cut nerves should be degenerated. 

 Ammonia and weak acids excite the muscle of the apex, whilst glycerine 

 which excites nerve, had no effect upon the apex. It must be inferred 

 that the heart-muscle has irritability and contractility independent of 

 the nerves in it. In the heart, stimuli pass in all directions from 



