90 



Scientific Proceedings (64). 



sure is greater, and in some cases there is actual raising of blood 

 pressure. 



Since there is no reason to suppose that the vaso-constrictor 

 center is the variable factor in the difference of vaso-constrictor 

 effect which was obtained, it is reasonable to assume that the 

 results are to be explained by the variation of the normal degree of 

 vaso-constriction present in the periphery at the inception of the 

 experiment. If the vessels were dilated, then reflex constriction 

 could occur to a great extent and aid in the retention of normal 

 blood pressure. If, on the other hand, the peripheral vessels were 

 well constricted, further constriction from trauma would be im- 

 possible and the compensatory effect being absent, the blood pres- 

 sure would fall. 



In other words, the effect of intestinal trauma upon blood 

 pressure is determined by the relative degree of constriction or 

 dilatation which exists in the periphery at the inception of the pro- 

 cedure. 



54 (986) 



Reflex cardio-inhibition in conditions of lowered blood pressure 



and " shock." 



By Holmes C. Jackson. 



[From the Department of Physiology, University and Bellevue 

 Hospital Medical College.] 



The experiments reported here represent a continuation and 

 amplification of those presented previously by Ewing and the 

 present author. 1 



In the first series, the accelerator fibers were cut in the dog in 

 order to remove accelerator effects as possible causes for the rise in 

 threshold value of the cardio-inhibitory reflex, observed in con- 

 ditions of low pressure (hemorrhage, etc.) where the rate of the 

 heart is increased. This factor can be excluded as the same results 

 were obtained as previously published. 1 The second series con- 

 sisted in an attempt to alter the blood supply of the medulla 



1 Ewing and Jackson, Amer. Jour. Physiol., 1914. 



