PROBLEMS OF MODERN SCIENCE 



The bones of the body serving for the support, 

 and in many cases for the shielding of the more 

 important and delicate soft parts, are particularly 

 liable to be affected by strains and stresses, as the 

 result of the resistance they offer to the effect 

 of the body-weight and to the pull exerted upon 

 them by the muscles. 



The thigh-bone may be quoted as an example 

 of a bone which in the standing position is con- 

 stantly being pressed upon by the weight of the 

 body, and is .frequently subject to the strain exerted 

 upon it by large and powerful muscles. A study 

 of the general architecture of a human thigh-bone 

 will be a convincing proof of its beautiful adapta- 

 tion to resist the forces to which it was subject 

 during the lifetime of the individual to whom it 

 belonged. 



The thigh-bone may be described as consisting 

 of an elongated column or shaft which expands 

 into two massive parts at either end. If it be cut 

 through in its length and the sectionised bone 

 examined, it is found that the columnar part or 

 shaft is occupied by a central cavity. This central 

 cavity, known as the marrow cavity, is filled during 

 life with soft marrow, and is a general character- 

 istic of a great many bones of the skeleton ; it is a 

 familiar feature of a so-called c marrow-bone ' of 

 an ox or a sheep. It will further be noticed that 

 the walls of the central or marrow cavity consist of 

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