BONE. 



92 ] 



BONE. 



portion of the section, a group of trans- 

 versely divided canaliculi are seen (fig. 72 

 a, a), without the lacunae to which they 

 belong, giving the substance a sieve-like 

 appearance. At the outer and inner surfaces 

 of the bones, the canaliculi terminate by 

 open mouths (fig. 70); and those nearest 

 the Haversian canals open into them. 



The contents of the lacunae are the same 

 as those of the cells of cartilage, viz. a trans- 

 parent, probably tenacious liquid, with a cell- 

 nucleus (fig. 71). 



If the cartilage of bone be boiled for two 

 or three minutes in water or a solution of 

 caustic soda, the nuclei are often rendered 

 very distinct. After macerating bone in 

 dilute muriatic acid, the lacunae, with longer 

 or shorter processes, become isolated and 

 appear as independent formations, resembling 

 stellate cells ; this phaenomenon probably 

 arises from the circumstance that the portions 

 nearest the lacunae are more resisting than 

 the rest, and less acted upon by the acid. 



In regard to the minute structure of bone, 

 independently of the lacunae and their cana- 

 liculi, a diy polished section exhibits a very 

 deUcate dotted appearance, which makes the 

 bone appear granular, as if composed of 

 closely aggregated pale granules, about 

 1-50,000 to 1-60,000" in size. This is best 

 seen in a transverse section. 



When bone is calcined and the residue is 

 rubbed between two pieces of glass, or when 

 bone is digested in a Papin's digester, minute 

 inorganic granules are left ; these are oval 

 or oblong, frequentlv angular, and are about 

 1-10,000 to 1-20,000" in diameter. 



Hence bone probably consists of an inti- 

 mate mixture of organic and inorganic 

 matter, in the form of minute, firmly-united 

 granules. 



The above remarks apply to human bones; 

 and those of the other Mammalia agree 

 essentially in structure with the former. 



In Birds, the Haversian canals are more nu- 

 merous and smaller than in the Mammalia, 

 and frequently run in a direction at right 

 angles to the shaft ; the lacunae are also more 

 numerous and smaller. 



In Reptiles, the Haversian canals are few 

 and veiy large, larger than in either of the 

 other classes ; the lacunae and the canaliculi 

 are also very large and the latter very nume- 

 rous. 



In Fishes, the structure is more uregular; 

 there are no concentric laminae; the Havers- 

 ian canals are sometimes absent, at others 

 very large and numerous ; frequently the 



lacunae are absent, whilst the canaliculi are 

 unusually long and elegantly wavy and 

 branched. 



The structures representing the bones in 

 the Invertebrata are noticed under the respect- 

 ive classes. 



The marrow or medullary tissue of bones 

 consists of ordinary fatty tissue, free fatty 

 matter, a particular liquid and cells, with 

 vessels and nerves, surrounded and traversed 

 by a small quantity of areolar tissue. Some 

 of the larger cells (?), found in foetal bones, 

 contain a large number of nuclei (fig. 73). 



Fig. 73. 



i)f i; 



a' 



Magnified 350 diameters. 



Peculiar granular cells, containing numerous nuclei, 

 from the very young marrow of the flat bones of the 

 human skull. 



When animals, especially young ones, are 

 fed with madder, the bones speedily acquire 

 a beautiful red colour, principally around 

 the Haversian canals, because it is here that 

 the process of formation of new bone is most 

 active ; and the earthy matter precij)itated 

 from the blood carries down with it the 

 colouring matter of the madder. 



The blood-vessels of bone which are dis- 

 tributed to the marrow (the nutrient vessels), 

 enter particular canals on their external siu*- 

 face; whilst those connected with the Havers- 

 ian canals are derived from the periosteum 

 and those of the marrow. The two sets ana- 

 stomose freely. 



Chemically, bone consists of gelatine, with 

 phosphate of lime, small quantities of carbo- 

 nate of lime, carbonate of magnesia, fluoride 

 of calcium, and sometimes a little oxide of 

 iron and magnesia. 



By digesting bone with dilute muriatic or 

 other acids, the inorganic matter is removed, 

 and by treatment with solutions of alkalies 



