196 ON THE COMPOSITION, STRUCTURE 



sist of the triple phosphate of Uine together with carbonate of limey 

 and a small quantity of phosphate and carbonate of magnesia. 



But we may proceed to analyze the bone by another method. If 

 we submit it to the prolonged action of dilute hydrochloric or nitric- 

 acid, then all the earthy matter is set free from the organic matter, 

 and still the bone retains its original form, but is now pliant. By this 

 means we preserve the organic constituents of bone separated from the 

 earthy matter. 



The next step in our enquiry into the structure of bone must be by 

 the aid of the microscope. A transverse, thin and transparent sec- 

 tion shows it to be perforated by numerous canals, each of which 

 gives passage to a blood vessel ; around eaeh of these canals, called 

 Haversian, as from a centre, we witness a number of concentric lamellae, 

 the position of which is marked out especially by certain bodies or 

 minute spaces, in shape somewhat like a melon seed, and known as 

 lacunae. Proceding from the margins or borders of these lacunse, 

 we notice a number of exceedingly fine waving lines, indicating the 

 presence of minute canals, termed canaliculi. 



If we make a thin section of the bone, parallel to its axis, we no 

 longer see the mouths of these Haversian canals with their surrounding 

 lamellee ; but we find the same canals running longitudinally, and the 

 lacunse presenting their longer axes. We observe also that these 

 canals communicate freely with one another, or in other words fre- 

 quently anastomise. We learn, from the presencej of these numerous 

 canals, that a free circulation exists in bone ; that while the blood, 

 as such, finds ready passage through the Haversian canals, the plasma 

 of the blood, or the blood without its larger particles ( the blood cor- 

 puscles) can be readily transmitted to the ultimate constituents of the 

 bony substance ; so that all and every particle of bone is so situated 

 as to be able to receive nutrition from the sanguineous fluid, and also 

 can remit into the general current certain portions of its waste. 



If we make a transverse section of bone, reduce it by grinding to 

 a transparent condition, and then, resting it upon a piece of platinum 

 foil, subject it to a degree of heat sufficient to dissipate the organic 

 matter ; we may observe, by the aid of the microscope, that the 

 lacunae have been rendered very indistinct, and that the canaliculi 

 have for the most part disappeared. If, on the other hand, we sub- 

 mit a transverse section of the same bone to the action of dilute acids, 

 nitric or hydrochloric, we shall find, on examination, that the lacunae 



