FURNITURE, AND ITS USES. 229 



fulfil its office in effecting that change in the 

 blood of which I am to speak presently. 



CAPACITY OF THE LUNGS. As to the 

 quantity of air which the lungs will hold, it is 

 very differently estimated. Many anatomists 

 think it about 200 cubic inches, or three 

 quarts, in the adult male ; but I think there 

 must be a mistake in their calculations, and 

 that it cannot exceed two quarts. 



When we breathe out, or expire, as it is 

 called, we do not expel all the air actually in 

 our lungs, but only a small part of it. Of 

 course when we inspire, we merely introduce air 

 enough to supply the place of what was before 

 expelled.* The amount which we draw or 

 inspire at each breath, (I speak of an adult 

 still,) is thought to be about forty cubic inches, 

 or over a pint ; but I think this estimate also 

 too high. Females, with lungs somewhat 



* It may be well to say here, that while the pro- 

 cess of inhaling air is called inspiration and that of 

 expelling it expiration, the whole process of breath- 

 ing is called respiration. 

 20 



