HEART OF TURTLE. 



57 



ulate the ventricle by an induction current, and after the current has 

 been removed the heart may pulsate for several minutes in a reverse 

 manner, each contraction originating at the stimulated place in the ven- 

 tricle, then after a pause the auricles, and finally the sinus contracting. 



2 



UJ 

 Q. 



Z 



o 



O 10 !0 30 40 SO 60 



MINUTES 



Fig. 35. — ^The full heavy line shows the average rate and duration of pulsation of 

 the hearts of 10 loggerhead turtle embryos (11 to 14 days old) in 0.7 per cent 

 NaCl. The dotted line shows the same things for the hearts of 10 embryos in 

 0.7 per cent NaCl+0. 1 per cent MgClj. It appears that the NaCl+MgCU does 

 not affect the rate, but nevertheless it stops the heart sooner than does the pure 

 NaCl solution. 



The heart of the loggerhead turtle often revives temporarily im- 

 mediately before it ceases to pulsate in solutions. This is seen in 

 figures 34 and 36, which show the decrease in the rates of pulsation of 

 the hearts of 20 loggerhead turtle embryos 11 to 14 days old. Ten of 

 these (fig. 36) were placed in 0.7 per cent NaCl, and 10 others 

 whose pulsation is shown in figure 34 were placed in 0.7 per cent 

 NaCl +0.1 per cent MgClg. The MgClj has no effect upon the raU, 

 but it stops the heart sooner than does the pure NaCl. (See fig. 35.) 



After the heart of the loggerhead turtle has ceased to pulsate in 

 NaCl it may be revived temporarily by CaClj. KCl will also revive 



