118 THE CONNECTIVE TISSUES, BY A. ROLLETT. 



earthy matters consist in proportions varying with the animal, 

 and the bone, of a mixture of carbonate of lime, of tribasic phos- 

 phate of lime and magnesia, of fluoride of lime, chloride of 

 sodium, arid traces of sulphates and of silica. The organic and 

 mineral constituents of the matrix of bone, which are thus 

 capable of being separated from one another, are so intimately 

 blended together both in moist recent and in dried bones, that 

 even with high microscopic powers no distinction can be per- 

 ceived between them ; such, for instance, as a granular precipi- 

 tate distributed through an organic basis. 



Tt has not been accurately ascertained whether the osseous 

 substance is composed of an intimate mechanical mixture of two 

 molecules, or of a complex double molecule.* In various as 

 yet imperfectly understood diseases (Rachitis, Osteomalacia), 

 the bones lose their mineral matters, and, undergoing other 

 concomitant changes, become soft, flexible, and capable of 

 being cut, whilst the bones of old people, with coincident signs 

 of atrophy (thinning, expansion of the cavities), become more 

 rich in mineral substances, less elastic, and at the same time 

 more brittle. 



The coarse morphology of osseous substance, as seen under the 

 microscope, consists then, as already mentioned, of plates, fibre- 

 like trabeculse, and superimposed lamellae. The appearances 

 presented in any particular case are dependent upon the osteo- 

 logical importance of the bone examined, upon the direction of 

 the plane in which the section is made, and upon the part of 

 this plane selected for examination. 



Osteologists, as is well known, arrange the bones into 

 different groups, as the long or tubular bones, flat bones, and 

 short bones ; and structural variations are met with correspond- 

 ing to these divisions. In the short bones and in the apo- 



* According to the younger Milne Edwards (Annal. des Sci. Nat., 4 S., 

 Tom. xiii., p. 113), different bones yield tolerably constant proportions 

 of os -em and bone earth. But the conclusions to be drawn from all pre- 

 vious analyses of bone are not in accordince with this statement. On feed- 

 ing animals with unusual diet, as, for instance, withdrawal of flesh from 

 the fjod of a carnivorous animal, even if the bones are coincidentally 

 supplied with non-nitrogenous material, they become poorer in salts. 



