96 ELECTRO-PHYSIOLOGY 



less which is no doubt attributable to the directly inimical 

 action of C0 2 . Experiments to the same effect have been made 

 with similar results on the excised frog's heart. When the air is 

 much attenuated (under the air-pump) the spontaneous pulsations 

 cease after about an hour, and the muscle loses its excitability to 

 artificial (mechanical or electrical) stimuli. If the air is 

 restored the pulsations begin again. Cyon, Klug, and Saltet (58) 

 showed the dependence of cardiac movements upon the presence 

 of oxygen in the frog's heart. It was filled alternately with 

 serum containing O, and serum saturated with C0 2 ; regular 

 pulsations occurred only with the oxygenated serum. Want of 

 oxygen therefore asphyxiates the heart as in ciliated cells of 

 unicellular organisms. This is principally due to paralysis of 

 the cardiac muscles from lack of oxygen, as witnessed in the 

 gradual disappearance of the spontaneous contractions of the 

 heart, together with a corresponding decrease in excitability to 

 artificial stimuli. 



It is highly probable that other nutritive matters carried by 

 the blood play a similar part to oxygen, while equally the 

 elimination of other D-products besides C0 2 is essential to the 

 preservation of excitability ; little, however, has yet been done in 

 the way of experiment. Martius ascertained for cardiac muscle 

 that serum-albumen had a marked effect in restoring depressed 

 action. When 0*6 / NaCl solution is circulated through a heart 

 that is beating spontaneously, or from artificial excitation, the 

 pulsations, at first vigorous, disappear almost entirely ; then, after 

 the heart has been brought to a stand-still, and shows no trace 

 of movement even with the strongest excitation, not merely 

 excitability, but even automatic activity, will return if blood and 

 serum, or even alkaline salt solution containing serum-albumen, 

 are run through the heart. Peptone and all other albuminous 

 bodies (syntonin, or albumen, casein, myosin) fail to produce 

 this effect. The exhausted muscle treated with these remains 

 absolutely unresponsive with even the strongest excitation, 

 whereas in every case, after circulation of blood or serum, it 

 recovered its beats, or spontaneous pulsations. These experi- 

 ments have not yet been tried on striated skeletal muscle. 



