BONES 



413 



well a8 the short and thick, bones exhibit upon their surface an osseous mass of a dense 

 nature, while their interior presents a cavity divided into small cellules by their bony 

 partitions. 



In reference to the composition of bones, we have to consider two principal con- 

 stituents : the living portion or the osseous cartilage, called osseiii, and the inorganic 

 or the earthy salts of the bones. 



The osseous cartilage is obtained by suspending bones in a largo vessel full of dilute 

 muriatic acid, and leaving it in a cool place at about 50 F. The acid dissolves the 

 earthy salts of the bones without perceptibly attacking the cartilage, which, at the 

 end of a short time, becomes soft and translucid, retaining the shape of the bones ; 

 whenever the acid is saturated before it has dissolved all the earthy salts, it should 

 bo renewed. The cartilage is to be next suspended in cold water, which is to be 

 frequently changed till it has removed all the acidity. By drying the cartilage 

 shrinks a little, and assumes a darker hue, but without losing its translucency. It 

 becomes, at tho same time, hard and susceptible of breaking when bent, but it pos- 

 sesses great strength. 



This cartilage is composed entirely of a tissue passing into gelatine. By boiling with 

 water, it is very readily convertible into glue, which passes clear and colourless 

 through the filter, leaving only a small portion of fibrous matter insoluble by further 

 boiling. This matter is produced by the vessels which penetrate the cartilage, and 

 carry nourishment to the bone. We may observe all these phenomena in a very 

 instructive manner, by macerating a bone in dilute muriatic acid, till it has lost about 

 the half of its salts ; then washing it with cold water, next pouring boiling water 

 upon it, leaving the whole in repose for 24 hours, at a temperature a few degrees 

 below 212 F. 



The cartilage, which has been stripped of its earthy salts, dissolves, but the small 

 vessels which issue from the undecomposed portion of the bone remain under the form 

 of white plumes, if the water has received no movement capable of crushing or breaking 

 them. We may then easily recognise them with a lens, but the slightest touch tears 

 them, and makes them fall to the bottom of the vessel in the form of a precipitate ; if 

 we digest bones with strong hot muriatic acid, so as to accelerate their decomposition, 

 a portion of the cartilage dissolves in the acid with a manifest disengagement of car- 

 bonic acid gas, which breaks the interior mass, and causes the half-softened bone to 

 begin to split into fibrous plates, separable in the direction of their length. According to 

 Marx, these plates, when sufficiently thin, possess, like scales of mica, tho property of 

 polarising light, a phenomenon which becomes more beautiful still when we soak them 

 with the essential oil of the bark of the Laurus Cassia. The osseous cartilage is 

 formed before the earthy part. The long bones are then solid, and they become hol- 

 low only in proportion as the earthy salts appear. In the new-born infant, a large 

 portion of the bones is but partially filled with these salts ; their deposition in the 

 cartilage takes place round certain invariable points of ossification, and begins at a 

 certain period after conception, so that we may calculate the age of the foetus accord- 

 ing to the progress which ossification has made. 



Composition of Bones, 



Heintz found that the fixed bases in the bones were sufficient to saturate completely 

 the acids contained in them, so that the phosphate of lime, as well as tho phosphate of 

 magnesia, which the bones contain, is composed according to the formula 3RO, PO 5 . 

 Bone phosphate of lime is, therefore, the tribasic or orthophosphate 3CaO,P0 5 

 (Ca 3 P-O s ). True bony structure is perfectly free from chlorides and from sulphates, 

 these salts being only found when the liquid pervading tho bones has potJgte com- 

 pletely removed. Tho bones in youth contain less earthy constituents tfl^^Kosc of 

 adults ; and, in advanced age, the proportion of mineral matters \nca^M, Von 

 Biria found more bone-earth in the bones of birds than in those of mammals ; ho 



