HISTORY. 



&quot; We gaze around; 



We read their movements ; we sigh ; and wl ile 

 We sigh, we sink, and are what we deplored.&quot; YOUNO. 



of the lungs. The blood is 

 r.dsed into the lungs by 

 one set of tubes or vessels 

 termed arteries, and passes 

 back by another set of vessels 

 termed veins. When the ribs 

 are raised and the floor of 

 the chest drawn down by the 

 muscles of inspiration, the walls of the chest fall in, or when they 

 are brought nearer together by the muscles of expiration, the due 

 proportion of air and blood is, by gentle pressure, sent out from 

 the interior of the lungs. A firm and elastic membrane lines the 

 inside of the chest, and the same membrane passing back, covers 

 in the lungs, forming their outer coat By this doubling of th 

 membrane, the lungs without being attached except at their roots, 

 where the lobes enter, are held by their own elastic action in cloa 

 contiguity to t&e chest, and thus they move freely with it* 

 movements. 



S3. The right lung is divided into three parts or lobes; the left lung is divide* 



into two lobes, between which is a 

 space where the point of the heart 

 lies. Each lung is contained in J. 

 email membranous bag called the 

 pleura, and the air-vessels whiah 

 axe connected with the windpipe, 

 through which we breatiie, run 

 along between the blood-vessels in 

 the lungs, and eo give to them 

 that quantity of air which is re 

 quired to change the colour of the 

 blood and to render it fit for cir 

 culation. The accompanying en 

 graving will serve to illustrate 

 the structure and position of t-he 

 lungs ; in the centre is a membrane 

 which divides the chest. The ribs 

 are cut of, so as to show the in 

 side of the chest. The diaphragm 

 which divides the chest from the 

 has been removed. Th 



