CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 41 



ganglion and the cerebral circulation shut off, no anemic increment is 

 obtainable. However, all other evidences of bulbar activity are present. 

 A vigorous corneal reflex is obtained prior to occlusion, and when the 

 clamps are adjusted, even though the level of pressure may remain more 

 undisturbed than that obtained under many minor manipulations, the 

 other symptoms of the asphyxial response are shown in full vigor. 

 There are marked respiratory spasms, skeletal convulsions, changes in 

 the pupils, etc. 



In marked contrast to such a picture are the effects when, from some 

 physiological disturbance, the medulla itself is thrown out of activity. 

 Here the effects of the interruption of functional continuity are opposed 

 to the effect of anatomical separation. Such a condition is present 

 while the animal is still profoundly under the effect of an occlusion that 

 has just been done, or even during recovery from occlusion, when the 

 functions of the brain stem are not yet fully established. If, under such 

 conditions, the animal is subjected to a renewed occlusion, no response 

 at all can be aroused. Generalized asphyxia, inflicted by clamping the 

 trachea and thus acting directly at the periphery is, in this condition, 

 also impotent to produce any effect. Under this general depression 

 there are no skeletal convulsions, no respiratory gasps, and pressure 

 changes are extremely slight, 5 or 10 mm. The heart just quietly runs 

 down. The condition of the eyes remains unchanged throughout. 



All the evidence of these experiments therefore would argue not only 

 for a normal release of the rise of blood pressure through the sympathetic 

 outflow, but also for a complete dependence of the activation of the 

 response on the integrity of the brain stem, and the maintenance of the 

 conditions of conductivity within it. The response transmitted by the 

 sympathetic system is functionally exactly on a par with all the other 

 physiological responses. When respiratory movements, eye move- 

 ments and skeletal reflexes are obtainable, the changes of blood pressure 

 can also be elicited. 



The anatomical relations of the splanchnic outflow in its bearing on 

 recovery after section of the spinal cord. The complete dependence on 

 the brain rather than on the spinal cord is well illustrated by experi- 

 ments on recovery of blood pressure from high section of the spinal 

 cord. Goltz, (17), (18) and later Goltz and Ewald (117) sectioned the 

 cord of dogs in the midthoracic region and found normal blood pres- 

 sure responses to subsist. These were attributed entirely to the con- 

 trolling influence of the cord over the sympathetic system. These 

 experiments have been repeated by later investigators, notably Sher- 



