MUSCULAR CONTRACTION 19 



Ca produces diastolic stoppage of the heart. In his conception 

 of the action of the " polarising " ions Mines was unduly 

 influenced by the work of Schulze and of Linder and Picton 

 on precipitation of arsenious sulphide sols. The relation 

 of valency to coagulation phenomena in hydrophile sols of 

 sulphur (Oden), lecithin (Neuerschloss), and gelatin (Loeb) 

 differs very considerably from that described by the Schulze- 

 Linder and Picton law, and gives evidence of antagonism 

 between divalent and monovalent ions which is suggestive in 

 relation to certain vital phenomena described below. Loeb's 

 work makes it very doubtful if the action of hydrion and trivalent 

 ions on membrane potential depend on the same mechanism, 

 and the degree of reversibility of the effects of one or the other 

 on the vertebrate heart reinforce this conclusion. As regards 



^ ■__^mi*"' 



,00 riqzo J\!u C/00 Cai ryzof^f^'^^ 



Fig. 7.— Effect of removal of calcium on the perfused heart of Pecten 

 (Mines, loc. cit.). 



the ** nomadic '* ions. Mines' hypothesis gives no explanation 

 of the opposed action of Na and K in certain cases and their 

 relative potency in others ; moreover, the extent to which these 

 ions are actually capable of penetrating the muscle cell is an 

 open question. 



Thecombining nature of theCa ion,on the other hand, finds 

 considerable confirmation in the work of Clark (19 12) on the 

 frog's heart, and is reinforced by very diverse lines of inquiry 

 into cell physiology which will be described in connexion with 

 ciliary activity. Clark showed that increase in the Ca/Na+K 

 ratio revives the amplitude of the frog's heart when it has 

 become diminished by prolonged perfusion, this loss being 

 associated with the removal of a substance of lipoid nature. 

 He suggests that Ca which precipitates lecithin, a normal 

 constituent of the cell membrane, maintains the normal semi- 



