THE HUMAN STRUCTURE 



91 



The analogy between the upper and lower limbs must be em- 

 phasised. It will only be noted here 

 that the humerus, with the clavicle and 

 the shoulder blade, forms the " scapular 

 belt " ; the femur, the longest bone in 

 the body, forms, with the ilium, the 

 " pelvic belt," stronger and less mobile 

 than the other, intimately connected 

 with the vertebral column and offering 

 a great resistance to movement. 



67. Resistance of the Skeleton, 



The compact part of the bones (of the 



diaphysis) was studied from the point 



of view of resistance by Wertheimf 1 ). 



He made use of human bones as fresh as possible : and worked by 



traction on prisms sufficiently homogeneous ; and he obtained 



for Young's modulus and the breaking stress R, the following 



results : 



Fio. 102. 



Frontal section of 

 the head of the femur 5 milli- 

 metres in front of the "neck."' 



Young's modulus has an average value of 2,300 kilogrammes 

 per square millimetre ; it is double that wxrich has been found 

 for pinewood of which the density is three times less than that of 

 bone ( 44). 



The average resistance to fracture by traction is 12 kilo- 

 grammes in the adult and 6 in an old man. Pinewood gives 

 figures a little less (8 kilogrammes). Wertheim's determinations 

 show a decrease in the feminine sex and with age ; which was 

 also observed by Rauber.( 2 ) . or.. 



'( l ) Wertheim, Annales de Chimie et de Physique, 1847, vol. xxi., p. 

 () A. Rauber, Elasticildt uni Festigkeit der Knochen, Leipzig, 1876. 



