The essentials of healthA text-book of anatomy, physiology, hygiene, alcohol, and narcotics . one, are filledwith a yellowish or reddish substance, called consists principally of fat cells and marrow marrow cells doubtless give rise to some of thered corpuscles of the blood. There are other sources oforigin for these corpuscles, but it is well established thatsome of them originate in this way. Microscopic Structure. If a longitudinal piece of bonebe ground very thin, and then examined with a micro-scope, a number of canals will be seen parallel to thelong axis of the bon
The essentials of healthA text-book of anatomy, physiology, hygiene, alcohol, and narcotics . one, are filledwith a yellowish or reddish substance, called consists principally of fat cells and marrow marrow cells doubtless give rise to some of thered corpuscles of the blood. There are other sources oforigin for these corpuscles, but it is well established thatsome of them originate in this way. Microscopic Structure. If a longitudinal piece of bonebe ground very thin, and then examined with a micro-scope, a number of canals will be seen parallel to thelong axis of the bone. These canals unite with eachother, as shown in Fig. 51, by short branches extendingacross nearly at right angles. A cross section of boneshows that these canals are circular or oval in shape, as THE BONES. L59 illustrated in Pig, 52, These are the Haversian canals,so called after their discoverer, Cloptin Havers. In theliving bone all these canals are filled with blood vessels,while the frequent communication of the canals permitsthe blood to tlow to all parts of the bone. But the most. Fig. 51. Longitudinal section of bone, showing the Haversian canals,magnified. interesting fact connected with the structure of bone isthat living cells are always present in them. The Bone Cells. Between the Haversian canals thereare oblong spaces, called lacunas, signifying a hole or alake. Extending from the lacunae in every direction,are minute canals, called canaliculi. In these irregular-shaped spaces are the bone cells. In Fig. 53 is a longi-tudinal section of bone showing these holes, with theirmany-branched canals extending from them. Fig. 52 isnot so highly magnified, but it represents the vast numberof these lacunae, with their canals leading from them. The lacunae are very small, yet the canaliculi aremuch smaller, being not over 2o~o~oo °^ an mc^ ndiameter. Yet in all these there is living matter, 160 THE ESSENTIALS OF HEALTH. the bone cells. These cells are nucleated, and are o
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysiology, bookyear1
