20 DYNAMICS OF LIVING MATTER 



parent and the heartbeat can easily be watched. When such eggs are 

 put into an Engelmann gas chamber and a current of pure hydrogen 

 is sent through, the heart may cease to beat in fifteen or twenty minutes; 

 the heart stops beating suddenly before the number of heartbeats has 

 diminished noticeably: it ceases beating before all the free oxygen 

 may have had time to diffuse from the egg. In one case the heart beat 

 ninety times per minute before the hydrogen was sent through; four 

 minutes after the current of hydrogen had passed through the gas 

 chamber, the rate of the heartbeat was eighty-seven per minute, three 



Fig. .. riG. 



IM 



»• ^ 



Fig. 4. ■ Fig. 5. 



Fig. 3. 



Figs. i-s. Liquefaction of the cell walls of the egg of Ctenolabrus due ^o lack of oxygen. 

 (From Nature.) The eggs were exposed to a current of hydrogen. The liquefaction of the cell 

 walls and the formation of droplets began when the egg was in the 8 cell stage (Fig. 2). 

 These droplets fuse into larger drops and finally nothing but these drops indicates the existence 

 of the germinal disk. Figures 2, 3, and 4, are drawn in intervals of 15 minutes. 



minutes later it was seventy-seven, and then the heart suddenly stopped 

 beating. It is hard to beheve that this standstill could have been 

 caused by lack of energy. Hydrolytic processes alone could furnish 

 sufficient energy to maintain the heartbeat for some time, even if all 

 the oxygen had been used up. The suddenness of the standstill at the 

 time when the rate had hardly diminished seenis to correspond much 

 more to a sudden collapse of the machine ; it might be that Hquefactions 

 or some other change of structure occurs in the heart or its ganglion 

 cells, comparable to that which we mentioned before. In another 

 fish, Fundulus, where the cleavage cells undergo no visible changes in 

 the case of lack of oxygen, the heart of the embryo can continue to 

 beat for about twelve hours in a current of hydrogen. In this case the 

 rate of the heartbeat sinks during the first hour in the hydrogen current 



