20 



Professor J. A. Mac William. 



chloroform-adrenalin reaction described by Levy and abundantly illustrated 

 in this investigation), intravenous injection of potassium salts, etc. In many 

 instances fibrillation has been induced by a small dose {e.g., 0"1 mgrm.) of 

 adrenalin and remedied by the intraventricular injection of a very large dose 

 (up to 1 mgrm.), the state of the heart and circulation remaining good after- 

 wards (fig. 12). The excitability and conductivity of the muscle are 



B. 



C. 



Fig. 12. — The upper tracing is from the left ventricle, the lower indicates the blood- 

 pressure. In A, fibrillation caused by faradisation with 1500 units lasted 6 minutes, 

 recovery following injection of 05 mgrm. adrenalin in three doses, B is shortly 

 after recovery. C, taken 1 minute later, shows much increase in the range of the 

 lever excursions. Note that the blood-pressure is still elevated. 



enhanced by a small injection and as early effects of a large injection ; 

 subsequently a pronounced depression of excitability occurs — shown in 

 many cases by a great diminution in responsiveness when tested by graduated 

 faradic currents; stimulation, that formerly induced fibrillation readily, now 

 fails to do so even when strengthened to many times its former intensity. 

 Diminished sensitiveness to faradic currents is often pronounced, while the 

 blood-pressure is still elevated and the heart is beating very strongly. 

 Adrenalin can thus act in two ways : (a) by reducing excitability, and (h) by 

 improving conduction. 



Hirudin. — Injections* (into the saphenous vein) of about 8-10 mgrm. per 



* Doses of 0*3-0'5 mgrm. were often effective in removing fibrillation injected into the 

 L.V. The solution of hirudin used generally contained 1 mgrm. in each cubic 

 centimetre of Ringer's fluid. 



( 321 ) 



