562 ACTION OF CURARE, ATROPINE, AND NICOTINE 



or the heart may be filled with the solution through a cannula. Both 

 these methods were used. 



It is furthermore necessary that the solvent is neutral or almost 

 neutral to the heart. Distilled water applied to the molluscan and 

 crustacean heart accelerates the rhythm and produces tonus contrac- 

 tions. It will therefore not do to use distilled water as the solvent. 

 Sea water is almost neutral to the heart of all the marine animals 

 worked on. It has a slight stimulating action but this appears very 

 gradually and only after long immersion of the heart in the sea water. 

 The solution of the alkaloids in sea water will in consequence give 

 fairly accurate results. A still better solvent is the blood plasma of 

 the animals themselves, and this was used in nearly all cases. I was 

 not able to obtain an artificial salt solution that proved to be neutral 

 to the heart of the pulmonates. A solution of the drugs in the blood 

 plasma was the only method available in the work on the snail and the 

 slug heart. 



The graphic method was used for recording the change in the heart 

 rhythm. 



Solutions of Curare, Atropine, and Nicotine of Sufficient Concentra- 

 tion to Affect Appreciably the Heart Have a Primary Stimulating 

 Action -The acceleration of the rhythm is followed by depression and, 

 if the concentration of the alkaloids is great, by complete cessation of 

 the rhythm, the heart remaining excitable to direct stimulation. 

 Nicotine is in every case the strongest stimulant. There does not 

 seem to be any great difference between the stimulating action of 

 atropine and that of curare. 



The hearts of the various invertebrates studied differ greatly in 

 their sensitiveness to the action of the drugs. In the weakest con- 

 centrations of curare the stimulating action appears in augmentation 

 of the rate and strength of the beats, and by gradually increasing 

 the concentration this augmentation passes into a condition of in- 

 complete tetanus. This tetanus may be maintained for 5 to 8 minutes, 

 especially in the heart of lamellibranchs and gasteropods and in the 

 gill ventricles of the squid. The relaxation is gradual and may be 

 accompanied by a feeble rhythm. After the rhythm has been abol- 

 ished by the action of a strong (1 per cent) solution of curare it can 

 usually be restored by bathing the hearts in plasma. This is not 



