BONE. 



BONE. 



in numerous longitudinal rows running par- 

 allel with the Haversian canals (fig. 67). 

 The general arrangement is, that the long 

 axis of the lacunae is parallel with the la- 

 minae in which they are contained, or be- 

 tween which they are situated. 



When the section coincides with the sur- 

 faces of a set of the lacunae, they present a 

 very elegant round or oval form (fig. 71), 

 irregularly surrounded by a perfect tuft of 

 canaliculi, which, being turned directly to- 

 wards the observer, appear more or less 

 shortened, and a small number of others, 

 which are diffused through the surface of 

 the lamellae. Here and there, in the thinnest 

 portion of the section, a group of trans- 

 versely divided canaliculi is seen (fig. 71 

 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. 69) ; and those nearest 

 the Haversian canals open into them. 



Sharpey's perforating fibres are calcified 

 pointed fibres, running from the periosteum 

 towards the Haversian canals ; they are ir- 

 regular and variable, and are best seen in 

 the bones of amphibia and fishes. 



If the cartilage of bone be boiled for two 

 or three minutes in water or a solution of 

 caustic soda, the bone-cells or protoplasts 

 and their nuclei are often rendered very dis- 

 tinct (fig. 70). After macerating bone in 

 dilute muriatic acid also, the lacunar 

 corpuscles, with longer or shorter processes, 

 become isolated, and appear as independent 

 formations. 



In regard to the minute structure of bone, 

 independently of the lacunae and their cana- 

 liculi, a dry polished section exhibits a very 

 delicate 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, frequently 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 

 essentially in structure with the former. 



In Birds, the Haversian canals are more 

 numerous and smaller than in the Mam- 

 malia, and frequently run in a direction at 

 right angles to the shaft ; the lacunae are 

 also more numerous and smaller, and the 

 canaliculi very tortuous. 



In Reptiles and Amphibia they are few 

 and very large, larger than in either of the 

 other classes ; the lacunae and the canaliculi 

 are also very large, and the latter very 

 numerous. 



In Fishes, the structure is more irregular : 

 there are no concentric laminse ; the Haver- 

 sian 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 re- 

 spective 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. 



In the foetal or red marrow, numerous 

 marrow-cells resembling the colourless cor- 

 puscles of the blood are met with; also 

 some comparatively very large or giant cells, 

 containing numerous nuclei (fig. 72) : K61- 

 liker's osteoclasts. 



Fig. 72. 



Magnified 350 times. 



Giant cells, or Myeloplaxes, 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 



