SOLID PARTS OF ANIMALS. 



alcohol and ether dissolve a small portion of it, which precipitates 

 again as the solution cools. 



Marrow from the thigh-bone of an ox was found by Berzelius 

 to be composed of the following substances : 



Pure marrow, . O96 



Skins and blood-vessels, . 0-01 

 Albumen, 



Gelatin, 

 Extractive, 

 Peculiar matter, 

 Water, 



0-03 



1-00 



From the preceding detail it appears, that pure marrow is a 

 species of fixed oil, possessing peculiar properties, and approach- 

 ing somewhat to butter in its nature. But it differs considerably 

 in its appearance in different parts of the body, owing chiefly, in 

 all probability, to a greater or smaller mixture of blood. 



CHAPTER V. 



OF SHELLS. 



UNDER the name of shells I include all the bony coverings of 

 the different species of shell-fish. For almost all the knowledge 

 of these substances that we possess, we are indebted to the im- 

 portant dissertations of Mr Hatchett. A few detached facts, in- 

 deed, had been observed by other chemists ; but his experiments 

 gave us a systematic view of the constituents of the whole class. 



Shells, like bones, consist of calcareous salts united to a soft 

 animal matter ; but in them the lime is united chiefly to carbo- 

 nic acid, whereas in bones it is united to phosphoric acid. In 

 shells the predominating ingredient is carbonate of lime, where- 

 as in bones it is phosphate of lime. This constitutes the charac- 

 teristic difference in their composition. 



Mr Hatchett has divided shells into two classes. The first are 

 usually of a compact texture, resemble porcelain, and have an 

 enamelled surface, often finely variegated. The shells belong- 

 ing to this class have been distinguished by the name ofporceta- 



