CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 29 



of pressure and no matter how exigent the inimical conditions. This is 

 well illustrated by the variation of pressure noted in figure 3. The pro- 

 tocol of cat 40 where pressure in maintained in excess of 60 mm. until 

 after a section of the spinal cord at the level of the 4th thoracic, also 

 emphasizes the relation of this level to splanchnic activity. 



On some anomalous curves. In a relatively large number of cats 

 (8 in 60) a depression of blood pressure was obtained on occlusion in- 

 stead of the usual anemic increment. This depression of the level of 

 blood pressure was great, approaching the order of magnitude of the 

 usual positive effect. In six of these cats, pressure fell 100 mm. and 

 more below the original level of blood pressure. Most of these curves 

 represented control occlusions, one example of which has been figured 

 (fig. 1, occlusion 1) in which no previous lesion had been inflicted the 

 vagi being intact in 'all cases. In one case, cat 24, also mentioned, 

 this depression appeared after low section of the spinal cord. In these 

 cats on occlusion there followed no initial increment, or only a very 

 slight increase in the level (5 mm.). Pressure then continued constant 

 foi some 20 seconds. Following this a great and very rapid fall of 

 blood pressure set in from which recovery occurred at about the time 

 ordinarily occupied by the second rise of blood pressure. In this recov- 

 ery from the low level of blood pressure, however, pressure approached 

 but never completely attained the original level observed before 

 occlusion. 



The magnitude of the effect might argue for the involvement of the 

 splanchnic system. As such, it might be aroused by an afferent excita- 

 tion of the depressor fibers in the vagus. The relation of the depressor 

 to the splanchnic system and also to the discharge of adrenalin (which 

 would of course be involved in all splanchnic excitation) has been dis- 

 cussed by Ludwig and Cyon (48) and Oliver and Schafer. Bayliss 

 (67) has dealt with the antagonism of asphyxia and depressor 

 stimulation. 



On the other hand, the depression of blood pressure, instead of being 

 due to the cardiac innervation set into action through an afferent chan- 

 nel, might be affected directly through a change in the minute volume 

 of the heart, especially under changed conditions within the vagus sys- 

 tem. Wickjvire (60) has particularly noticed that different degrees 

 of the depth of anesthesia gravely influence the changes in the level of 

 blood pressure due to the vagus system. 



II. RELATION OF THE ADRENAL GLANDS TO THE RISE OF PRESSURE 

 DURING CEREBRAL ANEMIA. The extensive involvement of the splanch- 



