SECT. 107.] OSSEOUS SYSTEM. 209 



disappearances of the tissue in all its parts, in consequence of chronic diseases, 

 paralysis, anchylosis, or as rarefaction of the osseous tissue analogous to 

 atrophia senilis, in syphilis, lepra, mercurial cachexy, paralysis, etc. Death 

 of the bones, necrosis, is observed in destruction of the periosteum, inflam- 

 mation of the latter, and of the bone, etc., generally, accompanied with an 



vssive growth of the parts still healthy. Peculiar derangements of nutri- 

 tion occasion osteomalacia and rachitis ; yet, in the former, the microscopical 

 investigation has afforded nothing worthy of being mentioned here. The 

 latter has been narrowly investigated by inyself and II. Meyer, and especially by 

 Virchow, and presents some conditions which arc worthy of being here consi- 

 dered. In the disproportionately large epiphysal cartilages, 1. the layer of the 

 ossifying cartilage-cells (the cells arranged in rows) measures 2'" to 5'", instead 

 of ;'"' ; 2. the border of ossification is dentated, the cartilage and the bone 

 variously locking into one another; 3. in well-marked, rachitic bones, the 

 granular deposition of calcareous granules at the border of ossification is 

 absent, and the cartilage-capsules are almost invariably transformed into 

 bone-capsules somewhat before ossification of the matrix, and likewise without 

 the formation of calcareous granules. It is on this account that the for- 

 mation of the bone-capsules is nowhere more beautifully seen than in this case 

 (see above). Upon the diaphyses the layer of the ossific blastema is much 

 thicker, ossifies, likewise, very slowly, and presents a partial formation of 

 cartilage. 



Accidental formations of cartilage and lone are very frequent. The former 

 tissue, notwithstanding that it is not regenerated, and that wounds of it heal 

 only by means of fibrous tissue, or, more rarely, by osseous tissue (ribs), pre- 

 sents itself abnormally in very many organs (bones, mammary and parotid 

 glands, testicles, lungs, skin), as the so-called enchondroma, and as a new cover- 

 ing upon the osseous growths at the border of worn-down articular extremities 

 (Uchcr). Accidental formation of bone appears in ossification of permanent 

 cartilages (ribs, larynx, epiglottis [very rarely] ), of tendons, upon the dura 

 mater and arachnoid, in the eye, ovary, in fibrous membranes (memoram 

 tibturatoria), in enchondroma, fibroid tumours and cancers, and in the lungs 

 (Mohr's cyst containing hairs). In these cases, also, the osseous substance is 

 not essentially different from the normal, and arises, sometimes from a carti- 

 laginous, sometimes, and, indeed, more frequently, from a soft blastema. 



For the investigation of the bones, well-polished sections, which may be 

 easily made, are of especial service. The investigation of decalcified bone 

 also well repays the trouble bestowed upon it. This may be obtained by 

 macerating a bone in cold diluted hydrochloric acid (1 part acid, 10 to 20 

 . parts water), till no precipitate is produced by ammonia in the fluid, which 

 should be frequently changed. With small pieces of bones, maceration for a 

 few hours is sufficient; but for entire bones, several days are required. 

 Sections of decalcified bone so prepared are to be made in all directions 

 with a sharp knife, and may be used especially for the study of the Haver- 

 sian canals and lamellae ; the latter can also be stripped off from the surface. 

 The bone-cells, also, are still visible ; their processes appear as fine striae, and 

 their nuclei come into view without farther preparation, but especially after 

 treatment with caustic potass, or after long boiling in water. After long 

 maceration in hydrochloric acid, or after long boiling in a sand bath or a 

 Papin's digester (Hoppe), the bone-cells themselves are obtained isolated as 



P 



