ITS COMPOSITION IN DISEASES. 33 



of a definite law indicating a relation between the density and the 

 proportions of organic and inorganic matters contained in the bone, 

 which is obviously a point of the highest importance. As, how- 

 ever, the proportions both of water and of fat contained in the 

 bone exert a great influence on its physical properties, and these 

 must necessarily be most intimately connected with its specific 

 gravity, it should be one of the first points in the investigation of 

 this subject to institute a comparison between the specific gravities 

 of different bones after being dried in the air, after the removal of 

 their fat, and in a perfectly anhydrous condition. The determina- 

 tion of the absolute weight has been almost as much neglected as 

 that of the specific gravity, in comparing together normal and 

 diseased bones, although it is only from this determination and 

 from a comparison with the specific gravity, that we can form a 

 judgment of the metamorphosis of matter going on in the bone 

 during any physiological or pathological process (and not from the 

 proportional numbers of a single chemical analysis). Although 

 we must presume that our readers are acquainted with the methods, 

 cautions, and modes of correction required for the determination of 

 the specific gravity, we would simply draw attention to the fact, 

 that the pulverised bone (in all conditions under which it may be 

 submitted to examination, whether it have been dried in the air, 

 deprived of its fat, or have been wholly freed from water) should 

 be kept for several hours in a vacuum after it has been well 

 shaken and impregnated with distilled water, such a precaution 

 being necessary for the thorough removal of all particles of air. 



Few observers, with the exception of Nasse and Stark, have 

 satisfactorily investigated the quantity of water contained in the 

 bones. Nasse was indeed induced to believe, from his observa- 

 tions, that the water contained in bones exerted no influence on 

 their hardness, but we cannot deny its influence in morbid bones 

 on this and other physical properties. As bone is very hygro- 

 scopic, we ought to notice the state of the thermometer and hygro- 

 meter in comparing the quantity of water present in different 

 bones which have been dried in air, before the pulverised bone is 

 thoroughly deprived of its water in an oil or air-bath. 



The determination of the quantity of fat contained in the bones 

 is more uncertain than that of most of the other constituents. 

 The fat, as we have already observed, is limited for the most part 

 to the medulla of the bones, extending only slightly into the 

 Haversian (or so-called medullary) canals. The fat which is not 

 contained in the cavities and interstices of the hones, but adheres 

 VOL. III. D 



