754 



DR FRASER ON THE PHYSIOLOGICAL ACTION 



Experiment LVII. 



A frog, weighing 460 grains, had its heart exposed by removing a small portion of the 

 sternum. It was acting at the rate of forty-eight beats per minute, while the respirations were 

 seventy-two. Five minutes afterwards, the heart was contracting at the rate of forty-five per 

 minute, while the respirations were seventy-four. One grain and a half of extract, suspended 

 in water, was injected under the skin of each thigh (three grains in all). 



In 



5 min.. 



heart = 36 



10 „ 



., == 28 



15 ., 



= 22 



20 ., 



., = 14 



25 .. 



., = 13 



30 .. 



., = 12 



40 .. 



.. = 10 



50 .. 



.. = 10 



1 h. ,. 



„ = 8 



1 „ 10 .. 



., = 8 



1 „ 15 ., 



.. = 



1 „ 20 ., 



.. = 



1 „ 30 „ 



.. = 12 



1 „ 40 ., 



„ = 12 



1 „ 50 ., 



•i = 12 



2 „ ., 



., = 10 



2 „ 30 „ 



,, = 8 



= 36 per mm. 



Contractions weak ; 

 and heart con- 



tinues dark dur- 

 ing systole. 



| Contractions very 

 J feeble. 

 Stopped in diastole 



Eespirations = 74 per min. 

 = 64 ,. 

 = 63 „ 



_ (" Frequent gasping move- 

 \ ments, which cannot be 

 = I counted. 



An occasional gasp. 

 ,, have stopped. 



,, Contractions irregular ; two auricular for one ventricular. 



These two experiments prove distinctly that Calabar bean has a direct influence 

 on the heart, that is quite independent of the indirect influence it exerts 

 on that organ by arresting the respiratory movements. Such arrest does, doubt- 

 less, assist the action on the heart, especially during the later stages of the 

 poisoning, by impeding the circulation ; and in mammals, when a small dose has 

 been exhibited, such comparatively slight diminution as is first produced in the 

 frequency of the heart's contractions must even be partly caused by the early 

 retardation and cessation of the respiratory movements that constantly occur. 



The cardiac action of physostigma is, thus, quite independent of the cerebro- 

 spinal nervous system, and is not a mere effect of the paralysis of respiration. It 

 must, therefore, be caused by an action of a direct nature on the cardiac ganglia, 

 which seem to be the only constant exciters of this organ, however its contrac- 

 tions may be regulated by other nerves. The peculiar changes that the heart's 

 action undergoes — the diminution in the frequency of its beats, then their stoppage 

 or irregularity, sometimes followed by renewal of rhythmical contractions, or of 

 independent movements in all the chambers, or in one only— prove that Calabar 

 bean first diminishes the vitality of the exciting ganglia, and then paralyses 

 them. Their influence is, at any rate, maintained until spontaneous movements 

 cease ; for, if we divide the ventricles from the auricles at a late stage of the 

 poisoning and when the contractions are unrhythmical, those chambers alone 



