THE HUMAN STRUCTURE 111 



78. Bust and Thoracic Co-efficient. If we compare different 

 persons, having the same stature, it will be found that the upper 

 half of the body, the bust, varies in size. The dimensions of the 

 bust are of importance on account of the organs it contains. They 

 are estimated by determining : 



1. The thoracic perimeter, taken at the level of the nipples ; 



2. The height of the body sitting, which is that of the bust, 

 the head being included ; 



3. The span or the horizontal length of the extended arms 

 (see Technics, 203, as to all these measurements). When the 

 bust is normally developed it has been found that the spread 

 exceeds the total height by about 4 centimetres. 



On the other hand, the relation of the height of the seated body 

 to the total stature is, on an average, 0'53 ; it is 0*5378 for 

 short people and - 5285 for tall ones. In the female sex these 

 proportions are slightly less. This relation 



g!* = 0-53 



Height 



is called the " thoracic co- efficient." 



From this point of view there are two characteristic types : 

 the people whose lower limbs are too long in comparison with 

 the bust, and those whose lower limbs are too short. M. Louis 

 Manouvrier ( l ) has called them . respectively "macrosoles" and 

 " brachysoles." The development of the thorax is therefore 

 independent of that of the legs. 



It can be easily observed in children that their limbs lengthen 

 disproportionately to the bust, which keeps its normal dimensions. 



The dimensions of the upper part of the body, measured in a 

 sitting position, are conditioned by the physiological functions 

 of the thorax. ( a ) The trunk encloses the axis of the body, the 

 vertebral column to which the heart and the lungs aie indirectly 

 connected. It is here that all human energy takes its rise. Hence 

 its development is greater in man than in woman. Man's mus- 

 cular power calls for intense respiratory activity. In woman the 

 digestive functions are predominant. 



79. The displacement of air that takes place in the lungs is pro- 

 portional to the thoracic amplitude. Its greatest value can be 

 determined by making a deep inspiration, followed at once by a 

 forced " expiration," all the air being ejected into a " spirometer." 

 Thus we can measuie what Hutchinson called " the vital capa- 



( x ) Louis Manouvrier (Mtmoires de la Soc. d'Anthrop. de Paris, vol. ii., 

 part 3, 1902). 



( 2 ) R. Collignon (Bull Soc. Anthrop, Paris, 1883). 



