516 



ON THE PHYSIOLOGICAL ACTION OF CASCA BARK. 



Time. 



Sudden alteration in character oP pu^se, 

 which becomes slow. The curve liat- 

 topped, and both systole and diastole 

 showing numerous secondary oscilla- 

 tions. Blood-pressure falling 



Blood-pressure rapidly falling .. 

 Both pulse and oscillations are very 

 irregular 



Tliere was no more pulsation after this ; 

 but the blood-pressure took 1 minute 

 30 seconds to fall quite to zero 



On opening the thorax the heart was 

 found moderately contracted ; elec- 

 trical stimulation of the phren'c nerve 

 caused contraction of the diaphragm 



Oscilla- 

 tions. 



mm. 

 3 

 4 



a 



40 

 30 

 25. 

 15 



The result of this experiment will be seen all the more clearly 

 by the following diagram, Fig. 160, in which they have been 

 graphically represented. 



The rise of pressure in this experiment was greater than in 

 any other in w^hich the cord had not been divided. This seemed 

 to us so extraordinary that we thought at first that the cord had 

 not been properly divided ; but a careful dissection made imme- 

 diately after death showed us that the division was complete 

 A year or two ago this result would have been regarded as a 

 proof that the drug acts on the vessels themselves ; but recent, 

 researches having shown that much more importance must be- 

 attributed to vasomotor centres in the cord and in the periphery 

 than was previously done, we cannot say whether the drug acts- 

 on these centres or on the walls of the vessels themselves. Tlie- 

 non-contraction of the vessels of the frog's web would indicate- 

 that the action of the drug is rather on nervous centres in the 

 cord or neighbourhood of the vessels than on the vascular walls^ 



