THE PULMONARY CIRCULATION. 



149 



resection of two or three ribs in the back, and a cannula was inserted 

 therein. Both the carotid and pulmonary arterial pressures were 

 recorded synchronously with mercurial manometers. 



Chauveau and Faivre passed a trocar connected with a manometer 

 directly into the pulmonary artery of the horse, through an intercostal 

 space, and without opening the thorax. This method, since the condi- 

 tions are absolutely normal, is far preferable, but it is only possible to 

 carry it out in large animals, such as the horse. 



The following determinations of the pulmonary arterial pressure, 

 with the chest opened, have been recorded : — 



There can be no doubt that these figures are lower than normal, 

 owing to the severity of the operative procedure, and to the necessity of 

 opening the thoracic cavity. 



By passing a cannula into the right ventricle, de Jager found the 

 intraventricular pressure to be equal to 27 to 59 mm. Hg. By Chauveau 

 and Faivre's method, which is free from the objections pertaining to the 

 other procedures, the relation of pulmonary to aortic pressure was found 

 to be as 1 to 3. If the aortic pressure in man be equal to 100 to 120 mm. 

 Hg, the pulmonary arterial tension is probably equal to 30 to 40 mm. Hg. 



In some experiments, conducted under conditions of artificial respiration 

 with the thorax open, Lichtheim - found that the greater number of the 

 branches of the pulmonary artery could he ligatured without lessening the 

 input into the left heart, or lowering the aortic pressure. After tying the left 

 pulmonary artery, and driving melted paraffin by Avay of the jugular vein into 

 the branches of the right pulmonary artery, Lichtheim even occluded as much 

 as three-fourths of the channels of communication between the right and left 

 hearts, and yet obtained no fall of aortic pressure. This result was not due to 

 any compensatory constriction of the systemic arterioles. 



Astounding as these experiments seem, yet their results are probably 

 entirely to be explained as due to the effect of artificial respiration. To 

 begin with, the capacity of the circulatory system of the lungs must be 

 very great in comparison with that of any other organ, for in a given time 



as much blood must stream through the lungs as through the rest of the 



body. Secondly, the high tension of the air artificially blown into the lungs 

 diminishes the capacity of the pulmonary vessels. So long, therefore, as the 

 vascular system is not reduced by ligature beyond that amount which is 

 rendered impervious by the artificial respiration, the aortic pressure will 

 not vary. The conclusion thus reached is that only about one-third of 



1 Sitzungsb. d. k. Akad. d. Wissensch., math.-naturw. CI., Wien, 1888, Bd. xcvii. 

 Abth. 3, S. 212. 



- " Die Storungen des Lungenkreislaufes," Berlin, 1876, S. 20. 



