LAWS OF BONE ARCHITECTURE 281 



Confirmatory data 



1. Agreement of analysis ivith breaking tests. The analysis of 

 the femur presented in the foregoing pages is in agreement 

 quantitatively with the work done on the femur experimentally 

 by Rauber (76) and by Messerer ('80). 



1. Breaking loads in tests on the femur made with testing 

 machines by Messerer, with the load applied at the head of the 

 femur and parallel to the axis of the bone were as follows: 



25-}^ear old woman 1350 kilos = 2970 pounds 



32-year old man 850 kilos = 1870 pounds 



78-year old man (heavy boned) 850 kilos = 1870 pounds 



82-year old woman 450 kilos = 990 pounds 



The calculated breaking load on the femur I analyzed in this 

 paper would be 5.68 times 320 pounds or 1820 pounds. (The 

 factor of safety being 5.68). 



2. The loads at the middle required to break the femur in 

 cross-bending tests made by Messerer are as follows: 



24-year old man 750 kilos = 1650 pounds 



26-year old man 875 kilos = 1930 pounds 



31-year old man 1300 kilos = 2850 pounds 



24-year old woman 1100 kilos = 2420 pounds 



25-year old woman 875 kilos = 1930 pounds 



The calculated breaking load in cross bending for the femur 

 I analyzed is as follows, based on an ultimate tensile strength 

 of 17,700 pounds per square inch; and an ultimate compression 

 strength of 24,000 pounds per square inch: 



In frontal plane 2000 to 3200 pounds 



In sagittal plane 2440 to 3310 jiounds 



The variations in the amount of the calculated load required 

 to cause breaking is due to the variation in the resisting strength 

 of the femur in the different planes about the axis of the femur. 

 There is very close agreement between these two series of 

 tests and the calculated strengths based on my analysis. This 

 agreement is as close as is to be expected in the case of other ma- 

 terials which are tested in a similar manner, such as steel, 

 wood, etc. 



