GENERAL KAPIDITY. 34:3 



laries of the lungs, and preventing the passage of blood. It 

 is a view pretty generally entertained, that in asphyxia the 

 non-aeration of the blood obstructs the pulmonary circula- 

 tion. We have already considered this subject rather fully 

 in treating of the general effects of arrest of respiration on 

 the circulation. The celebrated experiments of Bichat dem- 

 onstrated the passage of black blood through the lungs in as- 

 phyxia, and its presence in the arterial system. The experi- 

 ments of Dalton and others have shown that in this condi- 

 tion, the obstruction to the circulation occurs first in the sys- 

 temic capillaries, and the distention is propagated backward 

 through the great vessels and left cavities of the heart to the 

 right side. When the heart is exposed in a living animal, 

 and artificial respiration is kept up, arrest of respiration 

 produces engorgement and labored action of both sides. 

 There are no observations which show that increase of press- 

 ure in the pulmonary artery is the first and immediate result 

 of asphyxia. It is true, that after death the right side of the 

 heart is engorged; but it is well known, from observations 

 after death, and experiments on living animals, 1 that the 

 tonic contraction of the arteries is competent to empty the 

 blood into the veins ; and the facts just stated regarding the 

 insufficiency of the pulmonie sernilunar valves explain how 

 the right side of the heart may become engorged as the result 

 of obstruction to the blood-current in the left side. Estab- 

 lished facts seem to show that asphyxia does not primarily 

 affect the pulmonary circulation ; but that it is possible for 

 venous blood to pass through the lungs without undergoing 

 arterialization. 



General Rapidity of the Circulation. 



Several questions of considerable physiological interest 



arise in connection with the general rapidity of the circulation : 



1. It would be interesting to determine, if possible, what 



1 See experiments by MAGENDIE on the causes of the circulation in the veins. 

 Precis Elementaire de Physiologic, Paris, 1833, tome ii., p. 391. 



