DOSAGE OF THE MAMMALIAN HEART BY CHLOROFORM 75 
The frequency and regularity or the beat was usually quite unaffected both in 
auricle and ventricle, even when the beat was reduced nearly to extinction. 
V. 75 mgrms. CHC1, per Litre Modified Ringer's Solution 
(CHCl^ in '0075 P er cent - dilution) 
(Fig. 6) 
Under perfusion with this solution the amount of weakening of the auricle's 
beat varied in different observations between 64 per cent, reduction and practical 
abolition (temporary) ; the mean reduction in the cases observed was 79 per cent. 
The mean reduction of the ventricle's beat was 86*7 per cent. 
The solution usually took about fifty seconds to produce its full effect. 
Recovery was both in auricle and ventricle in all cases rapid and complete, even after 
prolonged perfusion with the solution, in one instance for twenty-two minutes 
forty seconds, during which time l,8oo cub. cent, of the CHC1, solution had 
flowed continuously through the coronary circulation. In this very instance both 
auricle and ventricle were beating fully normally within eighty seconds from the 
moment of discontinuance of the CHC1. solution. 
The frequency" of the rhythm of the beat remained quite unaltered by the 
CHC1 3 administration. 
VI. 50 mgrms. CHC1, per Litre Modified Ringer's Solution 
{CHCL in '005 per cent, dilution) 
(Figs. 7 and 8) 
Under this strength of CHC1, solution the weakening of the beat of the 
auricle varied from 30 per cent, reduction at outset of observations on Heart 20 
to 89 per cent, reduction in the later observations made on Heart 21. The 
average reductions in Hearts 5, 6, and 21 were 7 it per cent., 75 per cent, and 
74 per cent., respectively, but in Heart 20 it was only 30 per cent. In the other 
hearts administration of the solution for forty seconds sufficed to cause a weakening 
of 50 per cent. The recovery of the auricle was always rapid and complete. 
The weakening of the ventricle was in every case greater than that of 
the auricle, ranging from reduction of the amplitude of beat by 39 per cent, 
at outset of experiments on Heart 20 to extinction of the beat (temporarily) in Heart 5. 
In this latter heart, perfusion with the CHC1, solution for forty seconds sufficed to 
abolish (temporarily) the beat of the ventricle. But the ventricular beat neverthe- 
less returned rapidly and completely after perfusion continued five times as long as 
that. Three-minute doses of this solution caused progressively rather more and 
more severe effects, as repeated, while the experiment proceeded. 
The frequency of beat during the administration was never seen to alter 
from the rate obtaining when the chloroformization commenced. 
