The average weight in twenty-nine cases, male and female:
| Male. | Female. | |
| Right lung, | 24 ounces. | 17 ounces. |
| Left lung, | 21 ounces.,, | 15 ounces.,, |
| 45 ounces. | 32 ounces. |
The proportionate weight of the lungs to the body is:
| Male. | Female. |
| 1 to 37 | 1 to 34 |
The substance of the lungs is of a light porous spongy texture, and when healthy is buoyant in water. Specific gravity, 0.126; deprived of air, 1.056.
When pressed between the fingers, the lungs impart a crepitant sensation, which is accompanied by a peculiar noise, both effects being caused by the air contained in the tissue. On cutting the lung the same crepitation is heard.
The pulmonary tissues are endowed with great elasticity, in consequence of which the lungs collapse to about one-third of their bulk when the thorax is opened.
The root of each lung consists of bronchi, arteries, and veins, together with the nerves, lymphatic vessels, and glands, connected by areolar tissue, and inclosed in a sheath of the pleura.
Respiration consists of an expiration and an inspiration. The air passes in through the nose or mouth, through the larynx, trachea, bronchi, into the lungs.
Inspiration: By the contraction of certain muscles, the cavity of the thorax is enlarged; in consequence the pressure of the air within the lungs becomes less than that of the air outside the body, and this difference of pressure causes a rush of air through the trachea into the lungs until an equilibrium of pressure is established between the air inside and that outside the lungs. This constitutes inspiration.