34 OSTEOLOGY. 



The organic constituent of bone forms about one-third, or 33.3 per cent.; the 

 inorganic matter, two-thirds, or 66.7 per cent.: as is seen in the subjoined analysis 

 by Berzelius: 



Organic Matter, Gelatine and Bloodvessels . . 33.30 



/ Phosphate of Lime . . . .51.04 



Inorganic \ Carbonate of Lime .... 11.30 



or < Fluoride of Calcium . . . 2.00 



Earthy Matter, I Phosphate of Magnesia . . . 1.16 



\ Soda and Chloride of Sodium . 1.20 



100.00 



Some chemists add to this about one per cent, of fat. 



The relative proportions of the two constituents of bone are found to differ in 

 different bones of the skeleton, as shown by Dr. Owen Eees. Thus, the bones of 

 the head, and the long bones of the extremities, contain more earthy matter than 

 those of the trunk; and those of the upper extremity somewhat more than the 

 corresponding bones of the lower extremity. The humerus contains more earthy 

 matter than the bones of the forearm ; and the femur more than the tibia and 

 fibula. The vertebras, ribs, and clavicle contain nearly the same proportion of 

 earthy matter. The metacarpal and metatarsal bones contain about the same 

 proportion as those of the trunk. 



Much difference exists in the analyses given by chemists as to the proportion 

 between the two constituents of bone at different periods of life. According to 

 Schreger, and others, there is considerable increase in the earthy constituents of 

 the bones with advancing years. Dr. Eees states that this is especially marked 

 in the long bones, and the bones of the head, which, in the foetus, do not contain 

 the excess of earthy matter found in those of the adult. But the bones of the 

 trunk in the foetus, according to this analyst, contain as much earthy matter as 

 those of the adult. On the other hand, the analyses of Stark and Von Bibra 

 show that the proportions of animal and earthy matter are almost precisely the 

 same at different periods of life. According to the analyses of Von Bibra, 

 Valentin, and Dr. Rees, the compact substance contains more earthy matter than 

 the cancellous. The comparative analysis of the same bones in both sexes shows 

 no essential difference between them. 



There are facts of some practical interest, bearing upon the difference which 

 seems to exist in the amount of the two constituents of bone at different periods 

 of life. Thus, in the child, where the animal matter predominates, it is not 

 uncommon to find, after an injury to the bones, that they become bent or only 

 partially broken, from the large amount of flexible animal matter which they 

 contain. Again, also in aged people, where the bones contain a large proportion 

 of earthy matter, the animal matter at the same time being deficient in quantity 

 and quality, the bones are more brittle, their elasticity is destroyed, and, hence, 

 fracture takes place more readily. Some of the diseases, also, to which bones 

 are liable, mainly depend on the disproportion between the two constituents of 

 bone. Thus, in the disease called rickets, so common in the children of scrofulous 

 parents, the bones become bent and curved, either from the superincumbent 

 weight of the body, or under the action of certain muscles. This depends upon 

 some deficiency of the nutritive system, by which bone becomes minus its normal 

 proportion of earthy matter, whilst the animal matter is of unhealthy quality. 

 In the vertebra of a rickety subject, Dr. Bostock found in 100 parts 79.75 animal, 

 and 20.25 earthy matter. 



Form of Bones. The various mechanical purposes for which bones are employed 

 in the animal economy require them to be of very different forms. All the scien- 

 tific principles of Architecture and Dynamics are more or less exemplified in the 

 construction of this part of the human body. The power of the arch in resisting 



