CH. XXVII.] 



ASPHYXIA 



391 



last stage is mainly due to heart failure. If the vagi are not divided 

 previously, the rise of pressure is much less, and the heart beats very 

 slowly : this enables the heart to last longer, and is due to excitation 



of the cardio-inhibitory centre by venous blood. The accompanying 

 photograph of a tracing (fig. 304), which I owe to Dr C. J. Martin, 

 shows these effects; it has been somewhat reduced in size for 

 purposes of reproduction. The lower tracing is that of venous 



