CHAPTER IX. 



PECULIARITIES OF THE CIRCULATION IN DIFFERENT PARTS OF 

 THE SYSTEM. 



Circulation in the cranial cavity Circulation in erectile tissues Derivative circu- 

 lation Pulmonary circulation General rapidity of the circulation Time re- 

 quired for the passage through the heart of all the blood in the organism 

 Relations of the general rapidity of the circulation to the frequency of the 

 heart's action Phenomena in the circulatory system after death. 



Circulation in the Cranial Cavity. In the encephalic 

 cavity, there are certain peculiarities in the anatomy of some 

 of the vessels, with exceptional conditions of the blood, as re- 

 gards atmospheric pressure, which have been considered ca- 

 pable of essentially modifying the circulation. In the adult, 

 the cranium is a closed, air-tight box, containing the incom- 

 pressible cerebral substance, and blood ; conditions which are 

 widely different from those presented in other parts of the 

 system. On this account, some have gone so far as to con- 

 sider any change in the quantity of circulating fluid in the 

 brain, a physical impossibility. 1 Pathological facts in oppo- 



1 A number of years ago, there was considerable interest excited in the dis- 

 cussion of the possibility of an increase or diminution in the quantity of blood in 

 the brain under any circumstances. Monro, Abercrombie, and Dr. Kellie sup- 

 posed the quantity of blood in the brain to be invariable; Dr. Kellie assuming to 

 have proved this position by experiments which showed (according to his conclu- 

 sions at least) no diminution in the quantity of blood in the brain in animals 

 killed by hemorrhage, and no increase in the quantity in animals killed by a liga- 

 ture around the neck. He made other observations on this subject which it is un- 



