480 MOVEMENTS. 



Every bone, be it long or short, is composed of what is 

 called the fundamental substance, marked by microscopic 

 cavities and canals of peculiar form. The cavities contain 

 corpuscular bodies, called bone-corpuscles. The canals of 

 larger size serve for the passage of blood-vessels, while the 

 smaller canals (canaliculi) connect the cavities with each 

 other, and finally with the vascular tubes. Many of the 

 bones present a medullary cavity, filled with a peculiar 

 structure, called marrow. In almost all bones there are two 

 distinct portions : one, which is exceedingly compact, and 

 the other, more or less spongy or cancellated. The bones 

 are also invested with a membrane, containing vessels and 

 nerves, called the periosteum. 



The method usually employed in the study of the bones 

 is by thin sections made in various directions, and examined 

 either in their natural condition or with the calcareous mat- 

 ter removed by maceration in weak acid solutions. By the 

 first method, we can make out the relations of the funda- 

 mental substance, the direction and relations of the vascular 

 canals, and the form, size, relations, and connections of the 

 bone-cavities and small canals. By the latter method we 

 can isolate and study the organic and corpuscular elements. 



Fundamental Substance. This constitutes the true bony 

 substance, the medullary contents, vessels, nerves, etc., being 

 simply accessory. It is composed of a peculiar organic mat- 

 ter, called osteine, combined with various inorganic salts, in 

 which the phosphate of lime largely predominates. In ad- 

 dition to the phosphate of lime, the bones contain carbonate 

 of lime, fluoride of calcium, phosphate of magnesia, soda, 

 and the chloride of sodium. The relative proportions of the 

 organic and inorganic matters are somewhat variable ; but 

 the average is about one-third of the former to two-thirds of 

 salts. This proportion is necessary to the proper consistence 

 and toughness of the bones. 



Anatomically, the fundamental substance is arranged in 

 the form of regular, concentric lamellae, about -^^ of an 



