Anemia of Medulla Oblongata. 



157 



or two above the diaphragm or in the cord below the level at 

 which the highest fibers to the splanchnics leave the cord, argues 

 for the existence of a double functional pathway outside and 

 within the cord down which constrictor impulses may travel. 

 The level at which the highest fibers leave the cord is somewhat 

 higher than that given by the anatomical investigations of Langley, 

 Ranson, etc. While it varies from animal to animal it may run 

 as high as the second or third thoracic. 



The effect of adrenalin 



The work on adrenalin was preceded by a series of control 

 experiments in which the effect on the vasomotor response of 

 repeated occlusion in the same animal was worked out. It was 

 found that in intact animals, or in animals in which lesion of 

 the cardiac nerves had been inflicted, the constrictor effect could 

 be obtained practically indefinitely, the animal responding as 

 often as fifteen or twenty times in succession. Whereas neither 

 the intensity nor the time occupied by the response was greatly 

 affected, the contour of the blood pressure curve showed a con- 

 siderable change as the number of occlusions was increased. 

 Beginning with about the eighth or tenth occlusion, the curve was 

 found to dissociate into two essentially distinct constrictor 

 effects, each occupying about one half the time of the total effect. 



It was found that on tying off the adrenal glands in other 

 animals, no such number of repeated occlusions could be ob- 

 tained. These cats failed before the tenth occlusion, often much 

 earlier. Furthermore, after one or two responses following the 

 tying off of the glands, the response was much shortened and soon 

 came to occupy only about half the time of the normal response, or 

 less. It seemed to approximate the first half of the dissociated 

 curve of the exhausted, but otherwise anatomically intact animals. 



According to these data, adrenalin is involved in a double 

 relation to the splanchnic constrictor fibers. In the first place, its 

 increased secretion, which is thrown out after a considerable 

 latent period into the blood stream, is the agency that makes 

 possible the maintenance of the effect initiated by the splanchnic 

 fibers. These experiments seem therefore to demonstrate the 

 adjuvant nature of the emergency action of adrenalin long postu- 



