THE OSSEOUS SYSTEM. 385 



epiphysal cartilages, the layer of tlic ossifying cartilage-cells 

 (those disposed in rows), measured, instead of .',' ", 2 — 5'" ; 



2. that the ossifying border is toothed, owing to the circum- 

 stance that the cartilage and hone interlace in various ways; 



3. and lastly, that in decidedly rachitic bones, the deposition of 

 calcareous granular particles is wanting, and the cartilage-cells 

 almost invariably, shortly before the matrix, and also without 

 any appearance of calcareous granules, are metamorphosed into 

 bone- cells, on which account the formation of the latter can, 

 in no case, be so well studied as in these bones (vid. svpra). 

 Accidental cartilage- and bone-formations are very frequent. 

 The former tissue is met with, notwithstanding that it is 

 incapable of regeneration, and that wounds of it heal only 

 with a fibrous tissue, more rarely with bone (ribs), in very 

 many organs (bones, mammary glands, parotid, testicles, lungs, 

 and skin) forming what is termed enchondroma ; moreover, as a 

 new covering on the osseous growths, at the border of the worn 

 articular ends of bones (Ecker). The latter is seen in ossi- 

 fications of the permanent cartilages (ribs, larynx, epiglottis, 

 very rarely) of tendons (exercir-knochen, for example), in the 

 dura mater and arachnoid (Miescher, Rokitansky), in the eye 

 (Valentin), in the ovary, in fibrous membranes {membrana 

 obturatoria), in enchondroma, in fibrous and carcinomatous 

 growths, and in the lungs (Mohr's cysts containing hair). Even 

 in these cases the osseous tissue does not essentially differ from 

 the normal, and it is formed, sometimes from a cartilaginous, 

 sometimes, and in fact mostly, from a soft blastema (Yirchow, 

 1. c. p. 137). 



In investigations relating to the structure of bone, good 

 sections are, above all things, requisite. With a fine saw, thin 

 slices are made, which are ground with water upon a smooth 

 stone with the finger, or with a second smaller stone, for some 

 minutes (5 — 10), until they are rendered uniformly trans- 

 parent. The sections are then cleaned, and (the fat, if they 

 contain any, being removed by ether) may be employed, being 

 wetted with water, for the study of the Haversian canals and 

 disposition of the lacunae ; and with turpentine, for that of the 

 various lamellar systems. The lacuncc and their prolongations, 

 which, in sections, are dark and very distinct, owing to their 

 being filled with air, are completely filled by thin turpentine, 



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