PECULIARITIES OF BLOOD SUPPLY IN CERTAIN VISCERA 251 



unison with the artery. (2) Any change in the blood pressure of the 

 systemic venous system is immediately reflected in the blood pressure 

 of the sinuses of the brain and in the brain volume, (not well shown in 

 accompanying tracing). (3) A change never occurs in the vessels of 

 the brain which can not be accounted for by some change occurring 



Fig. 80. To show simultaneous records of the arterial blood pressure (A), the venous pres- 

 sure (B), the intracranial pressure (C), the pressure in the venous sinuses (D). The fall in ar- 

 terial pressure produced by stimulation of the cerebral end of the vagus will be found to cause 

 a fall of intracranial and cerebral venous pressure, accompanying that in the arteries, but a rise 

 in that of the venous system. (From Leonard Hill.) 



elsewhere in the vascular system outside the cranial cavity. This re- 

 sult is important because it shows that there can not be vasomotor 

 nerve control of the brain vessels. 



Taking into consideration not only the results of such experiments, 

 but also the peculiar physical conditions existing in the cranial cavity, 



