BONES. C 233 



and bile, are secreted to answer important purposes in the 

 animal economy ; others, as the urine, are separated from the 

 blood to be thrown out of the body as useless to the system ; and 

 others, as milk, for the nourishment of the young animals. To 

 these may be added certain foreign substances which make their 

 appearance in various parts of the body in consequence of dis- 

 ease. These being usually solid bodies have received the name 

 of morbid concretions. This important division will therefore be 

 divided into three parts, namely, 1. The Solid Parts of Animals ; 

 2.The Liq uid Parts ; and 3. Morbid Concretions. 



PART I. 



OF THE SOLID PARTS OF ANIMALS. 



THE solid parts of animals are very numerous, and many of 

 them hitherto have scarcely been examined. The following chap- 

 ters contain a general view of such of them as have hitherto 

 come under chemical investigation. 



CHAPTER I. 



OF BONES. 



BY bones are meant those hard, solid, well-known parts to 

 which the firmness, strength, and shape of living animals are in 

 some measure owing. In man, quadrupeds, and most other ani- 

 mals, the bones are situated below the other parts, and scarcely 

 any of them are exposed to view ; but in some of the tribes of 

 the lower animals, as the Conchifera and Mollusca, the bony por- 

 tion is placed on the outside of their bodies, evidently for de- 

 fence; In this case, they are distinguished by the name of shells. 

 In other animals, as lobsters and crabs, the external bony cover- 

 ing is called a crust. We shall treat of bones in the present 

 chapter, and of shells, crusts, and zoophytes afterwards. 



The bones in a human skeleton of mature age amount to about 

 200, not reckoning the teeth; but in extreme youth they are 



