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their discussion will belong more properly to the subject of 

 animal life, and to that part of it which relates to the laws of 

 muscular motion. 



13. The probable mode in which the oxygenation of blood 

 in the lungs takes place, may be thus briefly described: during 

 expiration^ capillaries which communicate with the air-cells imitate 

 the process of secretion, or else merely exhale an aqueous vapour; 

 during inpiration, these capillary, or exhalent, vessels become 

 filled with air, and by continuity of tubes convey air, or certain 

 properties of it, to the blood. 



G G 



