Vegetable Substances. , 275 



The following are all the substances which 

 have hitherto been found to exist in -vegetables. 



1. Sugar. 14. Fibrina. 



2. Gum. 15. Oil. 



3. Jelly. 16. Wax. 



4. Sarcocoll. 17. Resins. 



5. Tan. 18. Camphor. 



6. Bitter principle. 19. Caoutchouc. 



7. Narcotic principle. 20. Sandarach. 



8. Acids. 21. Gum resins. 



9. Starch. 22. Wood. 



10 Indigo. 23. Suber, or Cork. 



11. Extractive principle. 24. Alkalies. 



12 Albumen. 25. Earths. 



13. Gluten. 26. Metals. 



" The three last," Dr. Thomson judiciously 

 remarks, " are scarcely entitled to the name of 

 vegetable principles, it is highly probable," he 

 adds, " that they are taken up ready formed, 

 and deposited without alteration in the vegeta- 

 bles which contain them, whereas the other 

 twenty-three genera consist of substances which 

 owe their formation to the processes of vegeta- 

 tion." Of some of these, however, as the acids, 

 oils, and resins, we have been under a ne- 

 cessity of treating in the preceding lectures. I 

 shall, thereipre, not enlarge on them in this, but 

 content myself with a reference to the lectures 

 where they are to be found . 



1. Sugar is a substance which is contained 

 more or less in most vegetables. Some, how- 



