PRACTICAL ANATOMY. 



OSTEOLOGY. 



BONE. 



BONE is the hardest structure in the human body, 

 with the exception of the teeth. It is composed of one- 

 third organic and two-thirds inorganic matter. The 

 following table represents practically their relative pro- 

 portions : 



ORGANIC MATTER : Gelatin and blood-vessels, 33 parts. 



(Calcium phosphate,. . . 51 parts. 



Calcium carbonate, ... 12 parts. 



ii-.vrnj.a--.iv, ^AAAX^IV.V Calcium fluoride, . . . 2 parts. 



/ Magnesium phosphate, . 1 part. 



\ Sodium chloride,. ... 1 part. 



Externally, bone is pinkish white in color, while 

 within it is of a deeper red. It is covered with peri- 

 osteum, a fibrous, investing membrane, from which 

 it derives the vessels which supply it with nutrition. 

 Bone is also tough and somewhat elastic ; more so 

 in infants than in young adults ; while in old age it 

 becomes brittle. An analysis of the bones of the grow- 

 ing skeleton shows that they have a much higher per- 

 centage of organic matter and less of earthy than the 

 skeleton of a vigorous adult, while in old age the organic 

 matter is decidedly decreased and the inorganic or 

 mineral matter correspondingly increased. The propor- 

 tion between the organic and inorganic matter differs 

 also in the same skeleton ; thus, in the petrous portion 

 of the temporal bone there is an excess of earthy matter, 



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