156 Scientific Proceedings (113). 



the arterial circulation of the head. Occlusion in these experi- 

 ments was used essentially as a constant and powerful stimulus for 

 setting off a vasomotor response which was known to be aroused 

 by the medullary centers. The experiments were all done on 

 cats. Certain additional controls had to be obtained for the work 

 on the adrenals which will be described below. These experiments 

 were undertaken in connection with the studies on the functional 

 organization of the nervous system carried on by Professor F. H. 

 Pike and his collaborators. 



The splanchnic effect 



The evidence on the particular nervous channels involved in 

 the vasomotor response to asphyxia was obtained by testing the 

 response after the infliction of given nervous lesions. The 

 response was found to depend almost entirely on the constrictor 

 fibers of the splanchnic nerves. No lesion of the extrinsic cardiac 

 nerves significantly altered the response to occlusion. Injection 

 of curare, with the elimination of the pressor effect produced in- 

 directly by the skeletal innervation also did not modify the re- 

 sponse appreciably. However, section of the splanchnic nerves 

 immediately below the diaphragm abolished all vasomotor re- 

 sponse to asphyxia. 



It was possible to work out the pathway of the splanchnic 

 fibers with more precision. Section of the spinal cord in the 

 upper thoracic region was found to give the same effect as section 

 of the splanchnic in the region of the diaphragm; it also achieved a 

 complete interference with the vasomotor response on occlusion. 

 No other lesion within the splanchnic outflow, however, removed 

 the response. Section in the upper lengths of the sympathetic 

 chain, or section of the cord in any segment below the upper 

 thoracic, allowed the response to persist with only partial di- 

 minution. Since the two lesions which abolish completely the 

 asphyxial response are such as must definitely intercept all im- 

 pulses from the brain to the periphery, it seems that the splanch- 

 nic outflow is normally in intimate functional continuity with 

 the brain, and that all impulses for its release must arise physiologi- 

 cally within the medulla. The inability to abolish the response 

 completely by sections in the sympathetic chain only a segment 



