PHYSICAL ACTIONS OF THE LUNGS. 91 



general strainers and cleansers of the blood. Globule by globule 

 they discuss its problems, separate its truths from its errors and its 

 dead from its living, and hold it to its brief but energetic trials for 

 purification and the consequences which follow. 



Let us now turn from the act of expiration, from the air " laden 

 like a mule," as has been aptly said, "with a burden and baggage 

 of adulterations, and forced to carry them out," to inspiration — to 

 the newly-arriving air, the provision for supporting, and the blast 

 for rekindling, the blood. And let us spend a moment upon the 

 admirable means of nature for managing this very air, and present- 

 ing it to the blood in the last place, clear, genial, and warm. First 

 the nose, as the administrator of the sense of smell, takes cogni- 

 zance of any odorous or stimulating properties in the atmosphere, 

 and acts accordingly ; if pure, sweet, and fragrant, it draws in the 

 air by volumes, inspiring confidence and openness down to the very 

 air cells : if manifestly noxious or impure, the nose closes in propor- 

 tion, extemporizes a thousand valves that keep out the baser parti- 

 cles, and the air is driven against the sides of the passage, all the 

 way to the same cells, its uncleanly accompaniments being caught 

 in a viscid snarework all down the tube : it also gives notice to the 

 mouth, whose mucus catches its share of effluvia, which are rejected 

 by the shortest way. The mucus of these passages performs an im- 

 portant use, detaining clouds of particles which are unworthy to pass 

 inwards, and this operation increases in strictness the further the air 

 advances in the narrowing tubes. Consequently when it arrives in 

 the cells, it is clothed with kindly vapors issuing from the body, has 

 caught the tincture of the living heat, and is in fine unison with 

 the blood. And the blood has no sooner sniffed it well, than it again 

 becomes auroral and arterial. Immediately that this is accomplished, 

 the air, exhausted for this primary use, is spent, as we saw before, 

 upon the secondary and servile use, of undertaking and carrying 

 forth the dead exhalations. 



The blood that comes up to meet the air is all the blood in the 

 body, for after circulating, it all requires refreshment or purification. 

 It is carried into the lungs through the trunk of the pulmonary 

 artery. But we mentioned another artery, the bronchial, which 

 performs an office in the lungs. The old, exhausted and impure 



