igoo-i.] 



Obskrvations on Blood Pressure. 



209 



twenty seconds later the fall had been partly recovered from and the 

 pulse had resumed its former rate. A strong resemblance will be seen 

 between this tracing and one produced by either stimulation of the 



/■ 



.^V^^AVVWWVWWVl^^^/^. 



\WV\/^^ 



Tracing XXH.— 9/23.— No Morphia. 7 Chloroform pushed, dog being horizontal. 8 Sudden fall in 

 pressure with slowing of pulse. Chloroform continued and yet pressure normal again at 9. 



distal or the proximal end of the vagus, as shown in Tracing 23, and it 

 seems that all are agreed that such falls are of the nature of vagus 

 inhibition. Whether the vagus centres are directly stimulated by the 

 chloroform, or are more or less reflexly affected through afferent nerves, 

 or whether the stimulation is of the nature of asphyxia, it is hard to say. 

 From the fact that the fall disappears even if the chloroform be 

 continued, I would be inclined to agree with the Hyderabad Commission 



13a 



13 



Tracing XXHI. — 3/11 Dog horizontal. Left vagus previously divided, 

 stimulated by Faradic current. 13 Proximal end stimulated. 



Distal end of cut vagus 



that such is not a source of danger ; and as regards the nature of the 

 vagus inhibition, from the same fact, I would consider that it is caused 

 by strong vapour irritating the sensory branches of the vagus, and as 

 the sensory nerves become numbed the reflex disappears. It is not a 

 constant phenomenon, however, even when very concentrated vapour is 

 used. Another case from similar stimulation might show reflex 

 laryngeal spasm. The fact that these occasional, probably safe, falls in 

 pressure do occur in dogs is not sufficient ground in my opinion for 

 14 



