2&8 Chemistry. [Lecture 34. 



a brittle, hard, yellow substance, semi-trans- 

 parent like horn. It must have a near affinity to 

 gelatine, for by the action of nitric acid it is con- 

 verted into that substance ; and it consists of the 

 same ingredients, though probably in somewhat 

 different proportions. 



3. Fibrina is the solid or fibrous part of the 

 animal muscles. It is prepared in the blood, 

 from which it may be procured by washing the 

 red clot which forms in blood, when the serum 

 separates from it, till it has entirely lost its red 

 colour. It may also be obtained, by a similar 

 process, from the muscles or flesh of animals. 

 It is of a white colour, and has no taste or 

 smell. When exposed to heat, it contracts and 

 moves like a bit of horn, exhaling at the same 

 time the smell of burning feathers. In a stronger 

 heat it melts. It has a near relation to the two 

 former bodies, for nitric acid converts it into 

 gelatine. It appears also to be composed of 

 the same ingredients, but it probably contains 

 more carbon and nitrogen, and less of oxygen. 



4. Mucilage seems to be only the weakest and 

 most diluted form under which gelatine ap- 

 pears, and ought therefore to be referred to the 

 same head* 



5. Urea is the essential constituent of that 

 secretion (urine) from which it derives it name. 

 It differs from all other animal substances in con- 

 taining a larger portion of nitrogen. 



& S&gcur has been found in animads in every 



