144 ACTION OF DIGITALIS ON THE BLOOD-VESSELS. 



mum height of the wave 44, while in that taken when the 

 action of the digitalin was greatest, the mean pressure is some- 

 what over 90 millimetres, and the maximum 104. The fall of 

 pressure ought, therefore, to he more abrupt, but instead of this 

 it is more gradual. This alteration cannot, we think, be ex- 

 plained by any oscillations of the mercurial column indepen- 

 dently of the blood- pressure, and can only be due to contraction 

 of the arterioles retarding the flow of blood from the arterial 

 into the venous system during the cardiac diastole. In a recent 

 paper,* Boehm considers that the rise in blood-pressure pro- 

 duced by digitalis, is chiefly due to the increased action of the 

 heart, and that the condition of the arterioles has little or 

 nothing to do with it. He seems, however, to interpret tracings 

 of the blood-pressure in the arteries of mammals in the same 

 way as those obtained from the excised heart of the frog, and 

 apparently forgets that while in the latter the form of the 

 diastolic as well as of the systolic curve depends on the heart 

 alone, in the former the heart can have but little or no influence 

 on the pressure in the arterial system during the diastole, since 

 all communication between them is prevented by the closure of 

 the sigmoid valves. The curves which he gives confirm our 

 views, for tliey show the same gradual fall in the pulse-wave, 

 after the injection of digitalis, that ours do, and being traced 

 with Fick's spring-kymographion, are free from any fallacies 

 due to oscillations of the mercurial column. The continued 

 high pressure he observed during prolonged stoppage of the 

 heart, which he attributes to continuous cardiac systole, we 

 would ascribe to contraction of the vessels so far as it is not due 

 to changes in the respiration. If the arterioles were not con- 

 tracted the pressure would fall, as, e.g., in the experiments of 

 Ludwig and Hafiz.f 



We next attempted to ascertain whether the slowing of the 



figures. (These curves only show the ascent of the mercurial column above the 

 level in one limb of the U-tube of the manometer, whereas the true height is 

 got by adding to this the descent of the mercury below the level in the other 

 limb with a slight correction for the weight of the carbonate of soda solution in 

 the d» scending limb.) 



* Ffiiigers Archiv, vol. v, p. 190. 



f Ludwig's Arbeiien, 1870. 



