142 FORMATION OF THE ORGANIC MATTER. 



although in consequence of having heen deprived of 

 its organic matter, it will be found to be so brittle that 

 it may be broken down by very slight pressure. 



198. — Foi'iiiation of the organic matter. — The for- 

 mation of the organic matter is an operation quite 

 distinct from its impregnation with earthy material, 

 and the first part of the process may occur without 

 the last. The bone tissue may he formed, but if not 

 impregnated with earthy salts, it will be destitute 

 of those important physical properties for which 

 osseous tissue is required. It will be so soft, that it will 

 neither support (he weight of the body nor consti- 

 tute a firm framework for the the attachment of 

 muscles. 



199. Of the cancellated texture and compact tissue 

 of bone. — In some situations bone tissue is arranged 

 to form a texture exhibiting spaces or cancelli. This 

 is cal'ed the cancellated texture of bone. When 

 dried, cancellated tissue exhibits a number of spaces 

 like sponge, and has been termed spongy bone. In 

 the recent state, however, all the spaces are occupied 

 with fatty matter, traces of connective tissue, and 

 vessels, except in the case of birds, in which class, 

 with some exceptions, the spaces in the bones contain 

 air. The bony walls of tliese spaces are composed of 

 thin plates or spicules of osseous tissue, on the out- 

 side of which vessels are freely distributed. If the 

 bony walls of the cancelli become very much thick- 

 ened, so as only to leave room for one vessel in the 

 centre, we have an approach to the other kind of 

 bone tissue which is called crimpaet tissue. This, 

 however, in its perfectly formed state, contrasts re- 

 markably in charac er with the spongy cancellated 

 texture. The c impact tissue is so firm and dense 

 that you would not suppose it was travetsed by 

 numerous vessels which run in channels (Haversian 

 canals), and are connected here and there by trans- 

 verse branches, so that if the whole of the bony 



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