32 OSSEOUS TISSUE. 



nesia often occurs in larger quantities in the fossil remains of 

 vertebrated animals than in the fresh bones of the present animal 

 world. The greater abundance of fluoride of calcium which some 

 of our best analysts have found to occur in fossil bones has excited 

 considerable attention, more especially since Liebig* has shown 

 that even the cranial bones excavated at Pompeii exhibit a larger 

 proportion of fluoride of calcium than the bones of the present 

 generation (see vol. i, p 424). On the other hand, Girardin and 

 Preisscr have found that the fluoride of calcium had greatly 

 diminished in human bones which had lain long in the earth, and 

 in some cases had even wholly disappeared. There is thus sufficient 

 proof that it may increase as well as diminish in a perfectly normal 

 manner in the bones, although this increase or decrease cannot 

 always be referred to definite causal relations. Alumina, oxide of 

 iron, and silica, are substances which are very frequently found in 

 fossil bones, although we mast undoubtedly regard their presence 

 as due merely to infiltration. 



We shall consider the bones and cartilages of the invertebrate 

 animals in a subsequent portion of the work. 



The analysis of bones is undoubtedly one of the simplest opera- 

 tions of zoochemical research, but so many different methods have 

 been attempted that, notwithstanding the great number of analyses, 

 we have arrived at no conclusive results; we see, for example, that 

 the chemical composition of the phosphate of lime contained in the 

 bones is still doubtful, even at the present time. Thus, too, a 

 number of questions present themselves to our notice on entering 

 upon the consideration of the constitution of pathological bones, 

 which have either been wholly unanswered or very imperfectly 

 solved by the analyses in our possession. A more exact knowledge 

 of the specific gravity of the bones must have thrown considerable 

 light upon their physiological and pathological conditions; but 

 whilst in many cases, as for instance, in the examination of urine, 

 the density of the fluid to be analysed is in general more or less 

 accurately determined, the determination of this property has been 

 almost entirely neglected in the case of the bones, excepting in the 

 analyses made by Ragsky. Independently of the fact that the 

 density is an important physical property, deserving special atten- 

 tion in the consideration of the numerous modifications to which 

 the bones are subject in a healthy and morbid condition, we might 

 expect, by a careful study of the subject, to ascertain the existence 



* Die org. Ch. in Anwendg. auf Agric. u. Physiol. S. 140. [or English Trans- 

 lation, 1840, p. 156.] ' 



