and Observations on the component Parts of Membrane. 383 



water, been deprived of a great part of its gelatin, and is 

 nfterwards steeped in a dilute acid, the ossifying substance is 

 dissolved, and the cartilage remains, retaining the figure of the 

 original bone ; or, if a similar bone or piece of ivory, which has 

 not been boiled, is steeped in a dilute acid, (especially nitric 

 acid,) the ossifying substance is dissolved, and, at the same 

 time, but more slowly, the gelatin is separated, and causes the 

 liquor to become yellow, when the phosphate of lime is preci- 

 pitated by ammoniac. 



The cartilaginous body which remains, after the gelatin has 

 been thus separated, is not easily soluble in dilute acids, for 

 (according to its texture) many weeks, and even months, may 

 elapse, before a small part is taken up; but, in concentrated 

 nitric acid, or in boiling dilute acid, it is rapidly dissolved, as I 

 shall soon have occasion to mention. 



This substance, when dry, is semi-transparent, like horn, 

 and more or less brittle. 



It is the predominant and essential part, in the tissue or 

 web of membrane, cartilage, sponge, the horny stems of Gor- 

 gonics, horn, hair, feather, quill, hoof, nail, horny scale, crust, 

 and tortoise-shell ; and, although of similar chemical properties, 

 yet in consistency it varies, from a tender jelly-like substance, 

 to a completely formed membrane, or to an elastic, brittle, and 

 hard body, like tortoise-shell.* 



• These bodies, especially tortoise-shell, appear to be formed (as far as organic 

 arrangement is concerned) in the way of stratum super stratum. This structure is 

 peculiarly to be discovered after long maceration in diluted nitric acid ; for then, 

 tortoise-shell appears to be composed (like the black polished Gorgonia) of membra- 

 naceous laminae ; and the varieties of horn differ only by a tendency to the fibrous 

 organization. 



MDCCC. 3 D 



