64 



CONFORMATION AND ITS DEFECTS 



it does so by the ribs being drawn forward and outward, while at the 

 same time the intercostal spaces are enlarged by the separation of the 

 ribs one from the other. In contraction of the chest during expiration 

 these movements are reversed, the intercostal spaces becoming narrower 

 and the ribs being brought nearer together. 



The extent to which the chest is capable of enlarging is much greater 

 behind, where the ribs are long and loosely connected below, than in 



front, where they are shorter and more closely though 

 movably united to the breast-bone as well as to the 

 spine above. From these considerations it will be 

 seen that the power of expansion possessed by the 

 thorax is for the most part due to the length and 

 curvature of the posterior ribs, and it is for this 

 reason that ample scoj^e is so much desired in this 

 region. 



The points of special interest as affecting the 

 conformation of the chest are its dimensions in 

 respect to height, width, and length. 



Height. — The vertical diameter of the chest is 

 spoken of by hippotomists as its height. This 

 dimension, although regulated l)y the length of the 

 ribs, is not necessarily in exact conformity with it, 

 but will be greater or less for ribs of aiven length 

 according to their degree of curvature. The greater 

 the curve described by the riljs the less will be 

 the distance between their two extremities, and consequently the less 

 will be the vertical diameter of the chest; but it should be noted that 

 <xny diminution in the vertical distance resulting from their convexity 

 will be added to the transverse diameter, and thus what is lost in height 

 is gained in width. Ribs of moderate lenoth. Init wanting in curvature, 

 may give a fairly deep chest, but the sides will be flat and the capacity 

 of the thorax small in consequence. As Cline has observed, the more 

 the chest departs from a cylindrical form the less becomes its capacity. 

 Ample depth in this region is commonly denoted by the position of the 

 sternum, which should come well down below the point of the elbow. 

 This, however, is not always a reliable indication, as the position of the 

 chest between the fore extremities may be set higher or lower by the 

 muscles which suspend it, just as the height of the withers, as we have 

 seen elsewhere, may be influenced by the same cause. 



From what has been said it will be seen that it is of the first 

 importance to the beauty and utility of our subject that the ribs should 



Fig. 49. — Two Ribs, showing at 

 A A the Costal Cartilages 



