100 WdUrr SUipU'ij: 



serves to keep the lungs within the thorax and to prevent them 

 migrating to the neck. 



From the quadrupedal baboon thi'ough the semi-erect apes to erect 

 man, a jjrogressive comparative decrease in the rehitive size of the 

 fore-limb to the hind-limb is tn l)e observed. In other words, man's 

 arms are small compared with his legs ; the- fore-limbs of the baboon 

 are larger than its hind-limbs. The bal)oon shows on its thorax the 

 effect of bearing the weight of the l)ody. The neck of the elephant is 

 compressed by the weight of its head, the neck of swine by rooting, 

 the neck of man by his head weight. Compression of the neck de- 

 stroys the neck curves and curtails neck mobility. In man the neck 

 curves have been obliteirated, and the first ribs have become fully 

 curved. From these two causes the lung is permitted to rise in the 

 neck as the erect position has sunk the heart in the thorax and 

 displaced the lung upward. Lung in the neck has set up impulses 

 that cause cervical ribs to develop. Such development has occurred 

 in relation to the disappearance of progressive and other active uses 

 of the shoulders and arms of the upper limbs, and this fact explains 

 why cervical ribs are three times as common in women as they are 

 in men. 



As quadrupedal progression has been abandoned by all mammals 

 that have cervical ribs, and no quadrupedal mammal has cervical ribs, 

 it may be assumed that the crawling period of infancy is the great 

 factor that keeps the human neck true to type, or approximately true 

 to type ; for since the neck of seals keeps true to type, although its 

 fixed type is challenged every time it swims with its head beneath the 

 surface, a very moderate amount of quadrupedal exercise is evidently 

 sufficient to keep the neck true to type. 



The Unstable State which follows the Destruction of 

 the Mammalian Neck-type by Erect Bipedal 

 Progression. 



The migration of the lung towards the neck 'has led to a mass of 

 lung tissue being piled above the heart, and to an atrophy of the lower 

 thorax, hence the diaphragmatic base of the human lung is small in 

 comparison with the phrenic base of the quadrupedal mammalian lung. 

 As the functions of the lower thorax of man have been transferred to 

 the upper thorax, diaphragmatic breathing has become less perfect, 

 and costal breathing has begun to show up. Tliis change 

 has been caused by the erect position. Tho lightest organs 

 in the thorax rise to the top, which top, in man, is the widened 

 space between the first pair of ribs ; the sinking of the heavy heart 



