336 EXPERIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES. 



Blood containing much carbonic acid and little oxygen (crstick- 

 ungsUat), causes tlie vessels to contract and the stream to 

 become slow, while blood containing much oxygen and little 

 carbonic acid causes them to dilate. When different sorts of 

 blood are allowed to circulate after each other tlirough the 

 kidney, and each successive kind contains less 00^ than the 

 one preceding it, the rapidity of the flow from the vein goes on 

 increasing ; or, as it might be expressed, each kind of blood in 

 this series seems to diminish the amount of contraction of the 

 vascular walls which the greater amount of OO2 in the preceding 

 kind had occasioned. The order would be this — suffocation — 

 blood — venous — arterial — apnoeic, i.e., saturated with oxygen 

 by agitation with air. This dilatation, however, was onlv 

 temporary. 



When nicotine was mixed with blood in the proportion of 

 1 to 10,000 it seemed, at first, to cause contraction of the vessels, 

 for it produced a diminution in the flow of blood, and also in 

 the size of the kidney ; but both soon returned to the normal. 

 One per cent, of nicotine, on the contrary, seems to cause 

 immediate dilatation of these vessels, for it immediately causes 

 an increase in the velocity of ' the current and the size of the 

 kidney. The increased velocity is not to be entirely ascribed 

 to contraction of the vessels, for a solution of nicotine of this 

 strength alters the blood, and will diminish the friction in the 

 vessels. 



Atropia luis a powerful action, and different doses of it produce 

 different effects. In the proportion of 1 in 100,000 it causes 

 diminished rapidity in the flow of blood and in the volume of 

 the kidney, but both soon return to their normal. One in 

 10,000 causes diminished, followed by increased rapidity, but 

 this soon disappears. One in 5,000 soon kills the kidney, but 

 before doing so causes first diminution, and then acceleration of 

 the current through it. Chloral liydrate first causes diminished 

 and then greatly increased velocity, but it also has a very 

 peculiar action on the vessels, increasing the rliythmical con- 

 tractions in them when they are present, and causing them to 

 appear when they were previously absent. 



Tlie shocks of an induction coil, or Faradaic currents, do not 



