ELEMENTARY SUBSTANCES. 57 



6. Sulphur. In combination with other bodies^ sulphur 

 exists in considerable abundance in animal substances. It 

 can scarcely be said to occur in a separate state in animals ; 

 at least the experiments which may be quoted as encourag- 

 ing such a supposition, are by no means decisive. United 

 with oxygen, in the form of sulphuric acid, it exists in com- 

 bination with potash, soda, and lime. 



7. Fluoric Acid. BERZELIUS has detected this acid in 

 bones and in urine, in a state of combination with lime *. 



8. Muriatic Acid. This acid exists, in combination with 

 an alkali, in a great number of the animal fluidsj as with 

 soda and ammonia in urine. I have observed, that several 

 species of the genus Julus, when taken by the hand, emit 

 an odour so much resembling this acid, as to render the 

 opinion probable, that they secrete it, when irritated, in a 

 free state. 



9. Iodine. This interesting substance has been obtained 

 by Dr FYFE -f-, from the residue of the incineration of the 

 common sponge of the shops. The water in which sponge 

 had been infused, and which, consequently, contained its 

 gelatinous ingredient, yielded no traces of it. The portion 

 which remained, after infusion in water, or its albuminous 

 part, afforded, after being burnt to ashes, distinct traces of 

 its existence. We may conclude, therefore, that the iodine 

 is in combination with the albumen or insoluble portion. 

 In the sea-weeds, on the other hand, the portion which is 

 soluble in water contains the iodine ; thereby furnishing a 

 very striking point of difference in its mode of combination 

 in the Vegetable and Animal Kingdoms. 



10. Potash.-* This alkali exists in combination with the 

 sulphuric, muriatic, or phosphoric acids ; but it is far from 



* Annals of Philosophy, ii. p. 416. 



f " On the Plants from which Iodine can be procured."--Edin, Phil. 

 Journ. i. 256. 



