544 



MOVEMENTS. 



various directions and examined either in their natural condition or with the calcareous 

 matter removed by maceration in weak acid solutions. By the first method, we can 

 make out the relations of the fundamental 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 matter, called osteine, combined with various inorganic salts, in which the phos- 

 phate of lime largely predominates. In addition to the phosphate of lime, the bones 

 contain carbonate of lime, fluoride of calcium, phosphate of magnesia and of soda, and 

 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. 



FIG. 162. Vascular canals and lacunae, seen in a lon- 

 gitudinal section of the humerus ; magnified 200 

 diameters. (Sappey.) 



FIG. 163. Longitudinal section of "bone, from the 

 ^ aft of tit e human femur; 'magnified 180 di- 



ameters. (From a photograph taken at the United 

 a, a, a, vascular canals ; 5, 6, 6, lacunas and canaliculi in Btates Arm y Medical Museum.) 



the fundamental substance. 



This figure is introduced for the reason that it is a copy 

 of a photograph of the actual structure. 



Anatomically, the fundamental substance of the bones is arranged in the form of regu- 

 lar, concentric lamellae, about g-^Ys- of an inch in thickness. This matter is of an indefinite- 

 ly and faintly striated appearance, but it cannot be reduced to distinct fibres. In the long 

 bones, the arrangement of the lamellae is quite regular, surrounding the Haversian canals, 

 and forming what are sometimes called the Haversian rods, following in their direction 

 the length of the bone. In the short, thick bones the lamella} are more irregular, fre- 

 quently radiating from the central portion to the periphery. These peculiarities in the 

 disposition of the fundamental substance will be more readily understood after a descrip- 

 tion of the Haversian canals. 



The Haversian canals exist in the compact bony structure. They are either absent or 

 very rare in the spongy and reticulated portions. Their form is rounded or ovoid, the larger 



