. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. THORAX. 1037 same characters in both sexes. There is little difference in the height of the two apices. The elevation of the liver on the right side does not necessarily cause the right apex to be the higher. The right lung is more shallow than the left; but this is not because it is " pushed up," but because, in order to ac- commodate the liver, there is less lung- substance on the right side. If the mean of a series of observations represents the right side of the thoracic cavity as equal to 151, the left may
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. THORAX. 1037 same characters in both sexes. There is little difference in the height of the two apices. The elevation of the liver on the right side does not necessarily cause the right apex to be the higher. The right lung is more shallow than the left; but this is not because it is " pushed up," but because, in order to ac- commodate the liver, there is less lung- substance on the right side. If the mean of a series of observations represents the right side of the thoracic cavity as equal to 151, the left may be given as 182. The same may be said of both sexes. (b) Posterior region. — If we examine this region upon a cast of the thoracic cavity, we observe in the middle line a deep fossa, formed by the projection, to the very centre of the thoracic cavity, of the bodies of the dorsal vertebrae. This fossa is wider towards the base of the thorax, as may be seen by comparing the dif- ferent sections of the cast (compare the notches, 10, 11, and 12, with those of 3,4, and 5 \nfig. 668.). Fig. 668. '. Sections of a cast of the thorax showing the space encompassed by each pair of ribs respectively. The bodies of the thoracic vertebra, form almost a complete septum ; they are certainly a central column of support for the whole trunk of the body, bearing an equal distri- bution of the superincumbent weight in all directions. There is no part of the skeleton which more strikingly demonstrates that man was destined for the erect posture, than this central position, together with the increasing dimensions from above downwards, of the vertebral column. These conditions exist only in the human subject. The groove in the cast formed by the dorsal vertebra; is directed upwards and forwards, so that at the apex of the thoracic cavity it completely divides the lungs, producing two little cones laterally for the lungs, forming the right and left apex. At the base of the thorax this perpendicular
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