50 ON DIGITALIS, WITH SOME OBSERVATIOXS ON THE URINE. 



may be mentioned Kinglake, Briquet, Handfield Jones, Fnllei", 

 "VVinogradoff, and Traube. This opinion has been founded on 

 the observation that digitalis strengthens the weak and dilated 

 heart, and is injurious in hypertrophy, on the increase of the 

 arterial pressure often observed after its injection into the veins, 

 and on the contracted state of the ventricles found after death 

 constantly in frogs, but only occasionally in the mammalia. 

 Mosman thinks that it acts by diminishing the muscular irri- 

 tability of the heart, and thus lessening the number of pulsa- 

 tions without diminishing their force. Others believe that the 

 slowing of its action is produced through the nervous system, 

 and probably by an increased action of that part of it which 

 exercises a regulating influence. 



The settlement of these questions is of extreme importance, 

 in reference to the medicinal administration of digitalis, in cases 

 of weak heart. In order to their solution, let us consider what 

 would be the effect of increasing the muscular power of the 

 heart. Supposing that the size of the capillaries and the num- 

 ber and size of the waves of blood remained the same, but the 

 muscular power of the heart were increased, how would the 

 arterial tension be influenced ? 



The pov;er of the heart being greater in proportion to the 

 resistance it has to overcome, it would act with greater abrupt- 

 ness, and force the wave of blood more quickly into the arterial 

 system ; nnd as thus less blood would escape from the capil- 

 laries during the time of its systole, the arteries would be more 

 distended and the tension higher. This greater amount of 

 arterial tension, in its turn, would force the blood more quickly 

 through the capillaries at first, and the tension would rapidly 

 diminish ; but as the rapidity of the flow of blood would pro- 

 portionally decrease, the amount passing through the capillaries 

 in a ghen time would be much the same, and the mean arterial 

 tension much the same, but the oscillation much greater. If 

 now the capillaries be contracted, we will have the same 

 phenomena with a higher mean arterial tension, and if relaxed, 

 a lower tension. We would also say that when the capillaries 

 are contracted, less blood escaping by them during the systole, 

 there would be more surplus, and the height of the oscillation 



