CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 



17 



before inflicting any further lesions. Several successive sections of the 

 cord were frequently carried out in the same animal before occlusion 

 was produced. 



Section of the thoracic cord was carried out at various levels. The 

 effect of section varied considerably with the level of the lesion, and to 

 some extent also with the individual animal. Certain results, however, 

 are patent. Lesion in the lowest levels of the thorax elicited only a 

 slight permanent fall of pressure, and did not seriously affect the anemic 

 response. Lesions in the midthoracic, at the level of the 8th thoracic 

 and 9th thoracic vertebrae were more apt to elicit a profound fall of 

 pressure, and seriously to reduce the anemic increment. Lesions in 

 the upper thorax also elicited a great fall on section and often completely 



Fig. 3. Cat 30: cerebral anemia. Spinal cord sectioned at the level of the 5th 

 thoractic verterbra. This reaction shows the features of the typical blood vas- 

 cular response to anemia in every respect, but the level to which the maximal 

 rise of pressure (second rise) attains. The anemic increment here is only 50 mm. 

 Hg. Cardiac effects of slowing and acceleration recorded as usual. 



abolished the rise of pressure. There were, however, certain individuals 

 in which even a high thoracic lesion did not evoke a maximum fall of 

 pressure, and in which a relatively vigorous response was obtained even 

 after a high dorsal section. Accordingly the experimental material 

 can be roughly classified into three groups: 



Group I. Lesions in the lower thoracic region. Very vigorous responses 

 to cerebral anemia can still be obtained from animals with a lesion at 

 the level of the 10th to 12th thoracic vertebrae. Cat 25 with section 

 at T 10-11 showed an anemic increment of 125 mm. Hg. In cat 

 24 an anemic response lasting over 5 minutes was obtained, in which 

 the variation of pressure extended over 75 mm. Hg. The contour of 



