RELATIVE DIMENSIONS OF THE CHEST. 241 



82, and during deep inspiration 89 centimetres. The circumference at 

 the level of the ensiform cartilage is 6 centimetres less. In old people, 

 the circumference of the upper part of the chest is diminished, so that 

 the lower part becomes the wider of the two. The right half of the 

 chest is usually slightly larger than the left half, owing to the greater 

 development of the muscles on that side. The long diameter of the 

 chest from the clavicle to the margin of the lowest rib varies very 

 much. 



The transverse diameter in man above and below is 25-26 centi- 

 metres (97-1 0-1 inches), in females 23-24 centimetres (8'9-9'2 

 inches); above the nipple it is 1 centimetre more. The antero- 



Fig. 107. 



Curve taken with the cy rtometer Left side of the chest retracted in a girl twelve 

 years of age (Eichhorst). 



posterior diameter (distance of anterior chest-wall from the tip of a 

 spinous process) in the upper part of the chest is = 17 (6*6 inches), 

 in the lower 19 centimetres (7 f 4 inches). Valentin found, that in man 

 during the deepest inspiration the chest on a level with the groove in 

 the heart was increased about ^ to -f ; while Sibson estimates the 

 increase at the level of the nipple to be T V 



ThoraCO-meter. In order to obtain a knowledge of the degree of movement 

 rising or falling of the chest-wall during respiration, various instruments have 

 been invented. The thoraco-meter of Sibson (Fig. 108) measures the elevation in 

 different parts of the sternum. It consists of two metallic bars placed at right 

 angles to each other; one of them, A, is placed on the vertebral column. On B 

 there is placed a movable transverse bar, C, which carries on its free-end a toothed 

 rod, Z, directed downwards. The lower end of this rod is provided with a pad 

 which rests on the sternum, while its toothed edge drives a small wheel which 



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