0,2 PHARMACEUTICAL BOTANY 



parenchyma of seeds, fruits and the medullary ray cells and paren- 

 chyma of barks, roots and rhizomes. 



22. Volatile Oils. These are volatile odoriferous principles found 

 in various parts of numerous plants which arise either as a direct 

 product of the protoplasm or through a decomposition of a layer of 

 the cell wall which Tschirch designates a " resinogenous layer." 

 They are readily distilled from plants, together with watery vapor, are 

 slightly soluble in water, but very soluble in fixed oils, ether, chloro- 

 form, glacial acetic acid, naphtha, alcohol, benzin and benzol. 

 They leave a spot on paper which, however, soon disappears. They 

 respond to osmic acid, alkannin, Sudan III, and cyanin stains 

 similar to the fixed oils and fats. 



Volatile oils may be grouped into four classes: 



A. Pineries or Terpenes, containing carbon and hydrogen and 

 having the formula of doHi 6 . Examples: Oil of Turpentine and 

 various other volatile oils occurring in coniferous plants. 



B. Oxygenated oils, containing carbon, hydrogen and oxygen. 

 Examples: Oil of cassia and other cinnamons. 



C. Nitrogenated oils, containing carbon, hydrogen and oxygen 

 with nitrogen (from HCN). Example: Oil of Bitter Almonds. 



D. Sulphurated oils, containing carbon, hydrogen and sulphur. 

 Example: Volatile oil of mustard. 



23. Resins, Oleoresins, Gum Resins, and Balsams. These sub- 

 stances represent products of metabolism in many plants which are 

 formed either normally as Turpentine, Asafcetida, Mastiche, etc., 

 or as a result of pathological processes through injury to the plant 

 tissues as Styrax, Benzoin, Balsam of Tolu and Peru, etc. They 

 occur usually in special cavities such as secretion cells, glands, or 

 secretion reservoirs. 



Resins are insoluble in water but mostly soluble in alcohol. They 

 combine with alkalies to form soap. Many of them are oxidized 

 oils of plants. Examples: Guaiacum, Resina. 



Oleoresins are mixtures of oil and resin. Examples: Terebin- 

 thina, Terebinthina Canadensis. 



Gum resins are natural compounds of resin, gum and oil. Ex- 

 amples: Asafcetida, Myrrha, Cambogia. 



