LAWS OF BONE ARCHITECTURE 



213 



ultimate compressive strength of similar bone 18.95 kilograms per 

 square millimeter, or 26,850 pounds per square inch. 



The disproportion between the strength of compact bone in 

 tension and in compression seems to be general among the verte- 

 brates, as indicated by the following data, by Rauber: 



Fresh compact bone, man 



Fresh, compact bone, bullock.. 



Fresh, compact bone, calf 



Dried, compact bone, hog 



Dried, compact bone, wild hog. 



ULTIMATE STRENGTH 



Tensile <='°51P5'^'^- 



12.41 

 11.46 



8.93 



7.30 



10.29 



10.85 

 13.31 

 12.26 

 11.73 

 14.71 



0.73 

 0.86 

 0.73 

 0.62 

 0.70 



Figures are in kilograms per square millimeter. 



4. Shearing strength. The shearing strength of compact, hu- 

 man bone at right angles to the long axis of the bone is 11.85 

 kilograms per square millimeter, or 16,800 pounds per square 

 inch : the shearing strength of such bone parallel to the long axis 

 of the bone is 5.03 kilograms per square millimeter, or 7150 

 pounds per square inch (Rauber). 



5. Modulus of elasticity. Rauber gives the modulus of elas- 

 ticity of fresh, compact bone of the femur of a 46-year old man 

 as 1982 to 2099 kilograms per square millimeter, or 2,820,000 to 

 2,980,000 pounds per square inch. He also gives as the modulus 

 of elasticity for compact bone of the human tibia 1871 to 2041 

 kilograms per square millimeter, or 2,420,000 to 2,910,000 

 pounds per square inch. 



6. Torsional strength. The ultimate torsional strength of 

 compact bone varies, according to Rauber, from 4.0 to 9.3 kilo- 

 grams per square millimeter, or from 5700 to 13,300 pounds per 

 square inch. The ultimate torsional strength per square inch 

 for timber is 2000, cast iron 30,000 and steel 65,000 pounds 

 per square inch. 



7. Co7nparison of hone with other materials. The subjoined 

 table giving the strengths of various building materials, is de- 

 rived from the figures pubhshed in standard structural hand- 

 books. The figures for the strength of human tissues is derived 

 from liaul)er's woik. 



