28 CORA SENNER WINKIN 



to compromise the response by a definitive lesion. Such a lesion could, 

 it seems, be secured only when the section falls sufficiently far out in 

 the periphery or sufficiently high up in the cord, definitely to interrupt 

 the conduction pathways from medulla to coeliac ganglion. Unless this 

 interruption is accomplished, the fibers that are left in continuity with 

 the medulla and the periphery are able to initiate an anemic rise which, 

 even if considerably diminished in intensity, repeats all other char- 

 acteristics of the usual vasomotor response. 



To the splanchnic innervation, therefore, the most significant fac- 

 tors in the blood vascular reaction to cerebral anemia can be attrib- 

 uted: the initiation of the rise and the level which this reaches. Since 

 these factors can be controlled by differential lesions within the splanch- 

 nic system, the influence of the non-splanchinc vasomotors may be 

 neglected for the purposes of the present survey. 



On the influence of the splanchnic system on the maintenance of the 

 normal level of blood pressure: The splanchnic fibers seem involved when 

 the level of pressure is above 50 to 60 mm. for unless a complete interrup- 

 tion of the conduction path from medulla to coeliac ganglion has been 

 demonstrated, pressure returns to a higher level the height depending 

 apparently on the number of fibers in the splanchnic system remaining 

 functional. The level of 50 to 60 mm. is that shown by Mayer, Gouty 

 and later workers to be that maintained by the spinal cord alone. Yates 

 also finds this level to be approximately that reached by blood pressure 

 after recovery (2 to 32 days) from high transection of the spinal cord 

 at 8th cervical to 5th thoracic. Her average level of pressure lay some- 

 what lower than this, between 40 to 50 mm. From Pike's and Langley's 

 studies this residual spinal level appears rather as a skeletal or somatic, 

 than as a vascular or sympathetic phenomenon. 



The difference between the residual spinal level and the normal one 

 a difference of 80 to 100 mm. would therefore appear as accounted 

 for largely by the action of the sympathetic neurones within the splanch- 

 nic system. When the range of variation during anemia is examined, 

 this is seen to be three to four times as great in the animal with splanch- 

 nics intact as in the animal which is largely dependent on its skeletal 

 musculature. The variation of pressure in cats with low thoracic 

 section of the sympathetic chain is greatly restricted where the animal 

 was highly resistant to anemia and a period as long as 15 minutes elapsed 

 before the processes activated by the higher levels ceased. Further- 

 more, as long as the splanchnic system is functional, pressure does not 

 drop below the level of 50 to 60 mm. Hg., however great the variation 



