120 



DE, RUTHERFORD ON THE INFLUENGE OF THE VAGUS 



(b.) Cause of the Increased Blood-Pressure. 



During the operation of the cardio-inhibitory nerves, the work done by the 

 heart is diminished (see fig. 2). The rise in the blood pressure, which com- 

 monly follows section of the vagi, is therefore ascribed by all to increased force 

 and frequency of the heart's contractions. If this be the only cause of the rise 

 in the blood-pressure, then we ought to find that it undergoes no exaltation on 

 division of the vagi during a paralysed state of their cardio- inhibitory fibres. 



The following experiments were undertaken with a view to furnish an 

 answer to this question. Do accelerated cardiac action and increased blood- 

 pressure follow division of the vagi — during paralysis of their cardio-inhibitory 

 fibres — produced by such a substance as atropia sulphate ? — 



Experiments showing the Effect upon the Blood-Pressure and Frequency 

 of the Pulse which sometimes follows Section of the Vagi in Animals 

 where the cardio-inhibitory nerves are paralysed by sulphate of 

 Atropia. 



EXPERIMENT XX. 



-A Small Terrier Dog. 

 Trachea orEN. 



Caxula in Carotid Artery. 



Time. 



Pulse in 15". 



Mean Pressure in inches 

 of Hg.* 



General Notes. 



11-44' 



16 



4-5 





47' 



16 



4-5 





30" 







- 67 milligramme atropia sulphate 

 injected into vein. 



48' 30" 



40 



4-65 





50' 30" 



29 



4-2 





52' 



22 



4-4 





30" 







0'4 milligramme atropia sulphate 

 injected into vein. 



53' 



35 



4-2 





54' 



29 



4 





55' 30" 



25 



3-9 





56' 







Eight vagus divided in the neck. 



57' 30" 



23 



4 





58' 30" 







Left vagus divided in the neck. 



59' 



56 



5-9 





45" 



50 



5-9 





12 - 2' 



42 



6-4 





8' 



43 



8-45 





30" 







Distal end of left vagus irritated 

 by a strong induced current, but 







9 



no effect was produced on the 

 heart's action, clearly showing 

 that the cardio-inhibitory nerves 

 were completely paralysed. 



* In all these experiments Ludwig's Mercurial Kymograph was used. 



