48 



GENERAL ANATOMY. 



shall try to explain in speaking of the development and growth of bone. These 

 Haversian spaces are found chiefly in growing bones; but they occur also, 

 though in less number, in the adult bones. They have irregular jagged out- 

 lines, and the adjoining systems of lacunae and canaliculi are seen to be eaten 

 away by them. 



When the microscopic structure of bone was first demonstrated, it was 

 believed that the lacunae were solid cells, and their canaliculi solid processes 

 from those cells. Subsequently, when it was seen that the Haversian canals 

 are channels, which lodge the vessels of the part, and the canaliculi and lacunas 

 spaces by which the plasma of the blood, or the blood itself, circulates through 

 the tissue, it was taught that the lacunaa were hollow spaces filled during life 

 with that fluid, and only lined (if lined at all) by a delicate membrane. But 

 this view appears also to be delusive. Examination of the structure of the 

 bone, when recent, has led Yirchow to believe that the so-called lacunae are 

 really filled up during life with a nucleated cell, the processes from which pass 

 down the canaliculi. It is by means of these cells that the fluids necessary for 

 nutrition are brought into contact with the ultimate tissue of the bone. 



The animal part of a bone may be obtained by immersing the bone for a 

 considerable time in dilute mineral acid, after which process the bone comes 

 out exactly the same size and shape as before, but perfectly flexible so that a 

 long bone (one of the ribs is the usual example) can easily be tied in a knot. 

 If now a transverse section be made, the same general arrangement of the 

 Haversian canals, lamellae, lacunaa, and canaliculi is seen, though not so plainly 

 as in the macerated specimen. If the individual lamellae are examined, they 



are found to be composed of fibres, most 

 of which are nearly parallel ; but which 

 interlace together, and anastomose or 

 communicate with the fibres of the neigh- 

 boring lamellae. The organic or animal 

 constituents of a bone is only incompletely 

 removed by maceration, leaving the bone 

 for an indefinite period perfectly tough 

 and coherent; but after being long kept 

 in a warm dry atmosphere, or by incine- 

 ration in a furnace, the animal part may 

 be entirely removed, and then the earthy 

 constituent will retain the form of the 

 original bone, but on the slightest force it 

 will crumble down. The animal base is often called cartilage, but differs from 

 it in the following respects, viz., that it is softer and more flexible, and when 

 boiled under a high pressure is almost entirely resolved into gelatine. Carti- 

 lage does, however, form the animal basis of bone in certain parts of the skeleton. 

 Thus, according to Tomes and De Morgan, it occurs in the petrous part of the 

 temporal bone, and, according to Dr. Sharpey, on the articular ends of adult 

 bones, lying underneath the natural cartilage of the joint. 



Chemical Analysis. The organic constituent of bone forms about one-tliir'/, 

 or 33.3 per cent.; the inorganic matter, two-thirds, or 06.7 per cent.: as is seen 

 in the subjoined analysis by Berzelius: 



Fig. 19. 



Section of bone after the removal of the earthy 

 matter by the action of acids. 



Organic matter, 



Inorganic, 



or 

 Earthy Matter, 



Gelatine and bloodvessels 33.30 



Phosphate of lime 51.04 



Carbonate of lime 11.30 



Fluoride of calcium 2.00 



Phosphate of magnesia 1.16 



Suda and chloride of sodium . 1.20 



100.00 



Some chemists add to this about one per cent, of fat. 



The relative proportions of the two constituents of bone are found to differ 



