199 



and Dr Hales having filled the lungs with air, after 

 pouring water into the pulmonary artery of a calf, 

 observed the water to flow so freely into the bron- 

 chial cells, as to run out at the windpipe ; but the 

 vessels by which it escaped, were not large enough 

 to permit the colouring particles of the blood to 

 pass *. In like manner, injections will pass from 

 the pulmonary veins into the bronchia ; so that the 

 exhalent function in the lungs is carried on by the 

 whole system of pulmonary vessels. And, indeed, 

 if we reflect how much larger a portion of water the 

 venal blood (from the termination of the trunk of 

 the lymphatic system into the left subclavian vein at 

 only a short distance from the heart) must possess 

 in the lungs, than after it has passed those organs 

 and circulated through the whole body, we cannot 

 but admire this deviation from the ordinary laws of 

 the exhalent system, directed, as it is, to continue 

 and preserve, in sufficient abundance, an excretion 

 apparently so essential to the existence of living ac- 

 tion. 



157. These exhalent vessels of the lungs, like 

 those of the skin and intestines, appear to be endued 

 with a power, not only of exhaling water, but like- 

 wise of emitting carbon ; for water and carbonic 

 acid are expelled from the lungs in respiration, in 

 the same manner as they are produced by the skin 

 (147.) when in contact with atmospheric air. As, 

 therefore, the products of respiration and perspira- 



* Statical Essays, vol. ii. p. 72, 

 N4 



