THEORIES REGARDING ITS MODE OF ACTION. 71 



millimetres, attaining its maximum in two or three minutes, 

 and then gradually declining. 



Traube was thus lead to re-mould his theory, and to say that 

 at first there was stimulation of the musculo-motory as well as 

 the regulatory system, that the arterial tension was the product 

 of these two factors, and that digitalis finally paralysed both ; 

 and here the theory at present stands (as far as I can find out). 



When we look at Traube's first experiments, they certainly 

 seem perfectly conclusively to prove that digitalis acts through 

 the vagus, and this I certainly believe to be the case. Wino- 

 gradoffs denial of this is based on fallacious reasoning, assuming 

 as he does that because irritation of the vagi does not possess 

 the same action as injection of digitalis, therefore injection of 

 digitalis does not produce the same effect as irritation of the 

 vagi : whereas the action is the same so far as the latter goes, 

 but the former possesses the additional power of contracting 

 the capillaries, as Blake showed so long ago as 1839. 



Traube's theory also is very imperfect, for he makes the 

 arterial tension the product of what is really only one factor, 

 leaving altogether out of account the other equally important 

 one, the size of the capillaries, and, as I have stated before, if 

 the capillaries remain the same, and the number of cardiac 

 pulsations be diminished, no amount of force which each may 

 exert from stimulation of the musculo-motory power will do 

 anything whatever towards raising the arterial tension by the 

 diminished quantity of waves and consequent amount of blood. 



(2) The second theory, that of Messrs. Dybkowsky and 

 Pelikan, and (Kolliker ?) is that (a) digitalis exerts its action 

 directly on the regulating and musculo-motory apparatus in the 

 heart itself, and (b) not through the vagi, as their action is not 

 delayed or altered by destruction of the medulla oblongata or 

 division of the vagi, or by the previous administration of 

 woorari. The first part of this theory seems borne out by the 

 experiments of Eulenburg and Ehrenhaus on the extirpated 

 heart of the frog, which, when its lower third was immersed in 

 a solution of digitaline, had its motion completely stopped, if 

 the solution was strong, and if w^eaker it became slow and 

 intermittent. We see, too, that if we cut the vagus and irri- 



