394 GENERAL ANATOMY. 



other times the swelling results simply from the rarefaction of 

 the compact substance. The bone, which is less dense, and 

 more voluminous, has not then sensibly increased in weight. 

 I have in my possession a very fine specimen of this kind of 

 alteration, symmetrically occupying the two parietal promi- 

 nences in a skiill of a young subject: the bone, which is greatly 

 rarefied, is extremely vascular. These two kinds of tumefac- 

 tion, when they affect the long bones, sometimes determine 

 the contraction or disappearance of the medullary canal. This 

 case has been described under the name of enostosis.* I pre- 

 sented to the Faculty of Medicine a skeleton in which almost 

 all the bones present this alteration. 



620. Atrophy of the bones gives rise .prematurely to 

 changes similar to their diminution in old age. 



In the Museum of the Faculty of Paris, there are long bones 

 of a young man, in which the walls of the medullary canal 

 are as thin as paper. This canal has been enlarged by internal 

 absorption, while no formation has taken place at the exterior. 

 Phthisis, when very slow, sometimes produces this alteration 

 in the bones. It is also produced by long inaction. 



621. Inflammation of the bones is very imperfectly known. 



The term caries is one of the vaguest words in pathology. 

 The obscurity of the thing has been increased by comparing 

 caries to ulcers. What is most generally considered as ca- 

 ries, is a softening of the spongy substance of the bone, such 

 that it can be cut with a bistoury without injuring its edge. 

 This softening appears to be the effect of an inflammation, 

 which generally terminates by suppuration, and also sometimes 

 by necrosis. 



Rachitis is another kind of softening which appears to de- 

 pend upon the diminution of the earthy substance during the 

 period of growth, whence results the bending of the bones 

 under the weight of the body, and under the action of the 

 muscles. In fact, if the bones of rachitic persons be examined 

 at the period when they are soft,t it is found that the long 



* Lobstein, rapport sur les travaux executes a famphlth. d'anat. de Stras- 

 bourg, 1805. 



Stanley, in Med, Chir. Trans, vol. vii. Lond, 1816. 



