177 



mry organ, which, in reality, is not near so bulky as it appears, as may 

 be ascertained by examining the lungs, after all the air has been extract- 

 ed from them, by means of an air pump, applied to the trachea. 



Physiologists, for the most part, consider the bronchial arteries as the 

 nutritious vessels of the lungs. They assert, that as the blood which flows 

 along the branches of the pulmonary artery resembles venous blood, it 

 is unfit for the nutrition of the lungs, and that it was necessary that these 

 organs should be supplied by arteries arising from the aorta, and contain- 

 ing- blood analogous to that which is sent to every part of the body. But 

 though it be admitted, that this venous blood, brought from every part of 

 the body, and sent into the lungs, by their principal artery, may not be 

 tit to maintain the organ in its natural economy, this blood is' fit for that 

 use, when, after being made hot, spumous, and florid, by the absorption 

 of the atmospherical oxygen, it returns by the pulmonary veins, into the 

 left cavities of the heart*. 



Some have thought, that the blood which flows in the bronchial vessels, 

 exposed to the action of the air, ''like the portion of this fluid which tra- 

 verses the pulmonary system, Idst nothing of its arterial qualities, and 

 that, poured by the bronchial veins into the superior or descending vena 

 cava, it was a necessary stimulus for the right cavities of the heart, of 

 which blood entirely dark and venous, would not have awakened the con- 

 tractility. But even, if the experiments of Goodwin had not proved, 

 that the parietes of these cavities have a sensibility relative to dark blood, 

 by virtue of which, this stimulus is sufficient to determine their contrac- 

 tion, the action of the heart does not depend as closely as has been said, 

 on the impression of the blood on its substance, since it contracts, though 

 empty, and prolongs its contractions to relieve itself of the black blood 

 which fills it, when an animal dies of asphyxia. 



Boerhaave, who admitted one sort of peripneumony depending on the 

 obstruction of the bronchial vessels, whilst another, according to the same 

 writer, depends on the obstruction of the pulmonary vessels, seems to 

 justify, in some measure, the reproach, exaggerated unquestionably, 

 which some authors have thrown out against anatomy, of having rather 

 retarded than accelerated the progress of the Hippocratic practice of 

 medicine. The anatomical analysis of the lungs, or the distinction of the 

 tissues which enter into their composition, furnishes juster ideas on the 

 difference of the inflammations by which they may be attacked. It has 



* That the bronchial vessels exclusively nourish the lungs, is an opinion entertained 

 certainly by a majority of physiologists. When, however, we compare the size of these 

 vessels with the magnitude of the office assigned to them, it seems very doubtful whe- 

 ther they are adequate to it. We are inclined to believe notwithstanding what is al- 

 leged ag-ainst it, that the pulmonary arteries also contribute to the nourishment of the 

 lungs; and indeed there is a fact which almost proves it. We allude to the circum- 

 stance of the pulmonary adhesions, which are supposed to take place in consequence 

 of inflammation, having been repeatedly injected from the trunk of the pulmonary ar- 

 teries. Chapman. 



The circumstance mentioned at the conclusion of the preceding note, by no means 

 settles the dispute. We can throw coloured water or mercury into the trachea, and it 

 will flow into the pulmonary arteries, pulmonary veins, and bronchial arteries. Should 

 the material be thrown into the pulmonary artery, it will enter the pulmonary veins, 

 the bronchise and trachea. If it is thrown into the pulmonary vein, it penetrates the 

 bronchiis, and pulmonary arteries. Considering- the character of the membrane which 

 forms the texture of these organs, we cannot see any difficulty in believing- the bron. 

 chial arteries sufficiently larg-e to nourish the lungs. Godman. 



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