CARDIOVASCULAR CHANGES DURING CEREBRAL ANEMIA 5 



theorem. Mathison (42), (43) has shown the very much greater sensi- 

 tivity of the medullary over the spinal cells in their response to the 

 asphyxial agents such as increased CO2 or lactic acid, or decreased 

 oxygen. Pike and Scott (44) have discussed the regulation of H-ion 

 concentration in connection with the regulation of mammalian internal 

 environment. 



METHOD. In the present study advantage was taken of the rever- 

 sibility of the procedure of cerebral anemia. The ability to repeat the 

 initial stimulating effect of the insult on the medullary cells was ex- 

 ploited, rather than its abolition of conductivity within them. The 

 specific problems attacked were dealt with in terms of the intensity and 

 duration of the anemic rise, under given central and peripheral lesions. 

 A seemingly significant series of observations on the changes at the 

 periphery could be obtained by means of the pronounced differences 

 in the character of the curves recorded. 



Mayer (14) had called attention to the fact that the magnitude of 

 the vasomotor effect under asphyxia could be approached only by the 

 effect of compression of the thoracic aorta, or injection of strychnine. 

 From Mathison's work (42), (43), especially from his conception that 

 all forms of asphyxia are due to definite increase of the acid content 

 of the blood, cerebral anemia can probably be assumed always to be 

 acting at a maximum. The procedure followed was essentially that 

 indicated by Stewart (28). As here used, the emphasis lay especially 

 on the restriction of the occlusion time to as narrow a limit as possible, 

 in order to insure more rapid recovery. Accordingly, the shortest 

 possible occlusion period was uniformly employed and as a routine 

 procedure the head arteries were released as soon as the spontaneous 

 fall of pressure at the end of the response set in. 



The experiments were all carried out on cats. Ether was the anes- 

 thetic uniformly employed, and administered by tracheal cannula. 

 The purpose of the study was essentially to determine the degree of 

 involvement of the chief factors concerned, rather than their minute 

 evaluation. This has been left for subsequent study. The extensive 

 series of Stewart served as a basis of comparison and control. 



The head arteries were all secured outside the thoracic wall, the 

 branches of the left subclavian, separately secured in the axilla, the 

 right carotid, and right subclavian from within the carotid sheath in 

 the neck; the left carotid held the blood pressure cannula. All the 

 arteries were kept under ligatures ready to be occluded by clamps at 

 the convenience of the experimenter. Since there was no interference 



