CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 23 



this curve will be discussed below in connection with similar anomalous 

 curves obtained from control records in other animals. In these cats 

 a fall of pressure replaces the usual rise; the variation of level being 

 of the same order of magnitude. In cat 24, despite the great drop of 

 pressure, the original level was regained toward the end of the anemic 

 response at the time usually occupied by the second rise of pressure. 



Measurements of loss of pressure after section in the lowest levels 

 of the thorax show a maximal total loss of 50 mm. Hg. Frequently 

 only a few millimeters are lost. In cat 30 the 10 mm. lost after section 

 at the 10th thoracic were completely recovered within 10 minutes, 

 pressure rising even above the level recorded prior to transection. 



Group II. Abolition of the anemic response. Lesions of the cord 

 in the region of the 8th thoracic usually entail a rather severe effect; 

 the loss of pressure following this section may amount to 80 mm. Hg. 

 If the fall is as great as this, the anemic response is apt to be seriously 

 diminished. Cat 25, which gave a very vigorous response after section 

 at T 10, showed a further loss of 80 mm. when the cord was sectioned 

 at T 8, the level falling 100 mm. below that held when the animal was 

 intact. The anemic increment after section at T 8 was only 30 mm. 

 Hg. The reduction of the anemic increment to a variation of pressure 

 of only 30 to 40 mm. was seen in five other experiments, (cats 24, 30, 

 38, 40, and 42) in which section in the region of the 8th to 10th thoracic 

 gave a considerable depression of the level of blood pressure and in 

 which anemia of the bulb failed to evoke an increment of pressure 

 greater than 40 mm. That the vagus is partially responsible for this 

 effect is indicated by cat 42, in which an initial response after section 

 in the 8th thoracic gave an increment of only 20 mm. This increment, 

 however, rose slightly above 40 mm. in a subsequent occlusion after 

 the vagi had been sectioned. 



Section of the cord above the 8th thoracic in three animals, cats 35, 

 39 and 44, gave a very marked fall of pressure in all these cases and no 

 anemic response greater than 30 mm. was obtainable in any one of 

 them. In cat 44, only one section was made at T 6, and no anemic 

 increment at all was obtainable after occlusion. In the other two ani- 

 mals several successive sections were undertaken before occlusion was 

 tested. In cat 39, the first section was carried out at T 7; this was 

 followed by a fall of 55 mm.; 40 mm. more were lost in successive sec- 

 tions ascending to the level of T 4. In cat 35, 80 mm. were lost by 

 section at T 8, and only 20 mm. more by successive sections to T 6. 

 The level of pressure above base line from which only a minimal sub- 



