CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 43 



This relationship is of particular interest with respect to the appear- 

 ance of Traube-Hering waves. These have been noticed by all ob- 

 servers in the downward course of the final fall of blood pressure in the 

 anemic response. Whether nervous centers are no longer excitable to 

 sensory stimulation and whether or not the output of adrenalin is a 

 factor concerned, remains to be tested. It must, however, be borne in 

 mind that such a condition as this where Traube-Hering waves have been 

 elicited, is preceded by an intense activity of the splanchnic outflow 

 as stimulated by the medullary cells. 



In the disturbance of the internal medium which the excessive con- 

 centration of carbon dioxide in the occluded cerebral vessels brings 

 with it, the increased rate of flow is carried out and maintained by the 

 vascular musculature, and some product of adrenal activity probably 

 makes possible the maintenance of the increased impetus given the 

 blood flow through such a prolonged period of time. However, it is 

 only by virtue of the neurones within the central nervous system that 

 the response is initiated, that it is regulated by changes in the cardiac 

 musculature, and finally that the response is carried out as an integrated 

 whole. The retention of a constant tension of carbon dioxide in the 

 blood by means of an adaptive blood vascular reaction, is therefore 

 mediated in the mammal through its higher central nervous organiza- 

 tion, particularly the cells within the medulla oblongata. 



To Prof. F. H. Pike the writer is greatly indebted for suggestions, 

 advice and criticism, extended throughout the research. 



CONCLUSIONS 



1. The nerves of the heart are not essential either for the activation 

 or for the persistence of the characteristic pressor phenomena of the 

 anemic rise. 



2. In the early stages of cerebral occlusion the cardiac innervation 

 functions as a check on the rapid rise of blood pressure. In this modera- 

 ting action, accelerators as well as vagi are involved, since on excision 

 of the stellate ganglia, the vagi alone are unable to prevent an abrupt 

 and steep rise of pressure. 



3. The activation and maintenance of the vascular response under 

 cerebral occlusion is controlled essentially by the splanchnic nerves. 



4. Differential section in various regions of the splanchnic outflow 

 influences the level of the arterial blood pressure. The extent to which 

 the pressure falls on section is an approximate index of the degree to 

 which the anemic rise will be compromised by the lesion. 



