376 D. OGATA AND SWALE VINCENT 



sensory nerves of the skin, too, depends mainly on the constric- 

 tion of the blood-vessels in the same area,^^ and Hofmann^^ 

 writes: ''The rise of blood-pressure on stimulation of sensory 

 nerves is produced by the constriction of the blood-vessels of 

 abdominal organs as in asphyxia. At the same time the blood- 

 vessels of the brain, skin, and muscles dilate, as a rule, and an 

 increase of the volume of limbs takes place." Thus the splanch- 

 nic area plays a principal part in the reflex changes of blood- 

 pressure on stimulation of the somatic as well as the splanchnic 

 nerves. 



We have made some experiments on this point, and can con- 

 firm the above statements. The dogs had both vagi cut and 

 were under morphia and curare or brain compression, and the 

 sciatic or saphenous nerve was stimulated with induction shocks. 

 The volume changes of the limbs (hind and fore) and of the 

 abdominal organs (small intestine, kidney, and spleen) were 

 recorded. 



The rise of blood-pressure, when sufficiently high, was always 

 accompanied by a remarkable diminution of the volumes of 

 abdominal organs and a pronounced dilatation of limbs (fig. 18). 



The pronounced fall of blood-pressure with weak stimulation 

 when the animal was under brain compression was seen to be 

 accompanied by a distinct increase of the volume of the intes- 

 tine. Thus it appears clear that a reflex rise and fall of blood- 

 pressure on stimulation of a somatic nerve (sciatic, saphenous) 

 is brought about chiefly by constriction and dilatation of the 

 blood-vessels in the splanchnic area. 



9. SUMMARY 



1. In dogs under ether or chloroform, stimulation of sensory 

 nerves (saphenous, tibial, peroneal, sciatic, ulnar, and median) 

 causes usually increased respiratory movements when narcosis is 

 not profound or curare is not employed. These increased move- 

 ments produce a fall of blood-pressure, and when they are very 

 violent, one cannot obtain any pressor reflex even with a strong 

 stimulation. When much increased respiratory movements are 

 prevented by very deep narcosis or brain compression, fall of 



