THE OSSEOUS SYSTEM. 341 



the growth of a bone in thickness, plays the principal part in the resto- 

 ration ; of course by means of the exudation poured out from its vessels. 

 In animals, entire bones of the extremities, and ribs are regenerated, 

 pretty nearly in their original figure, not only when the periosteum has 

 been saved, of which many examples are exhibited in Heine's collec- 

 tion in Wurzburg, but even after entire excision with the periosteum, a 

 rudiment of the bone is reproduced (Heine). In man also, a good many 

 instances have been afforded of the reproduction of entire bones, such 

 as the lower jaw, the ribs, the scapula (Chopart) ; and the cases of 

 isolated, in some instances large, portions of bone being so regene- 

 rated are very numerous. It is especially the diaphyses, which are 

 readily replaced, when they have been lost in one way or another, less 

 frequently the spongy bones and spongy parts of bones, and those of 

 the cranium ; in the latter, however, openings made by the trephine 

 are in many cases filled up, instead of fibrous membrane, with isolated 

 patches of bone, or even with an entire piece of bone ; in fact, trephined 

 portions of bone have united exactly in the same way as has been ob- 

 served to take place with portions of bone half cut off (Pauli). Hyper- 

 trophy of bone assumes the most various forms, all of which may be 

 reduced under two principal types : 1, deposits on the surface, or ex- 

 ternal hyperostoses, which are formed chiefly from the periosteum ; and 

 2, internal or scleroses, which consist in the filling up of the medullary 

 cavities and Haversian canals with new bone, and these two forms may 

 occur either separately or combined. The former takes place in inflam- 

 mations of the periosteum, either idiopathic or in connection with cancer, 

 arthritis, syphilis, &c., the latter not only consecutively in old age, but 

 also in rachitis, osteomalacia, and syphilis. With respect to the micro- 

 scopic conditions of these growths, Virchow deserves the credit of hav- 

 ing distinctly indicated ("Archiv, f. Pathol. Anat. I.," p. 135), that 

 the bony growths or osteophytes on the cranium are formed by a direct 

 ossification of connective tissue without any preliminary development 

 of cartilage, which is also undoubtedly the case in the filling up of the 

 losses of substance in the cranium, in regeneration proceeding from 

 the periosteum, and in most cases of sclerosis. The newly formed os- 

 seous substance is sometimes like the normal (many exostoses), some- 

 times more dense, with small vascular spaces and large irregular lacunae. 

 Atrophy of the bones is shown in their disappearance in totality in 

 consequence of chronic diseases, paralysis, anchylosis ; or in rarefaction 

 of the osseous tissue analogous to senile atrophy, in syphilis, lepra, 

 mercurial cachexy, paralysis, &c. Death of bone (necrosis) is observed 

 in cases where the periosteum has been destroyed ; in inflammations of 

 that membrane and of the bone, &c., for the most part attended with 

 an excessive growth of the remaining sound parts.* Peculiar morbid 

 conditions exist in osteomalacia and rachitis, but in neither of these 



* [In necrosed bone, the bone-corpuscles are generally but little changed; the inter-cor- 

 puscular structure is granular and of a dark color. DaC.] 



