4 DEFINITIONS 



They do not all contain nitrogen. A few are alkaloidal, but most 

 are neutral. 



Resins are solid plant substances or exudations usually acid in 

 character, insoluble in water, soluble in water and an alkali. The 

 definition of the pharmaceutic class — " resins " — is those plant 

 products soluble in alcohol and insoluble in water, obtained either as 

 a residue from the distillation of an oleoresin or by pouring a concen- 

 trated alcoholic extract of the drug into water or acidulated water. 



If they occur mixed with a volatile oil they are termed oleoresins. 



Gum Resins are mixtures of a gum and a resin or oleoresin. 



Gums are desiccated exudations obtained by incising the limbs 

 and branches of certain plants. They form a mucilage or jelly with 

 water, and are insoluble in alcohol. The most important are acacia 

 and tragacanth. 



Balsams are natural products differing from oleoresins in con- 

 taining benzoic or cinnamic acids to which the delightful odor is 

 due. Chief are Tulu and Peru. 



Resinoids are principles soluble in alcohol, insoluble in water. 

 They are often mixtures containing true resins. 



Oils. These occur as fixed and volatile or essential. An oil is 

 a substance which greases, which leaves when dropped on a cloth a 

 stain which water will not wash out, a stain whieh makes paper 

 translucent. They are termed fixed or volatile, according to the 

 permanency of this stain on warming, characters clearly defined by 

 the names given the two groups. If a drop of the oil is placed upon 

 paper and warmed over a flame, the stain disappears if it is a 

 volatile oil, while if a fixed oil, the stain remains. A very simple 

 test is the action of a ground glass stopper, of a bottle containing the 

 oil. The stopper of a bottle of fixed oil rotates easily and quietly in 

 the neck, whereas a volatile oil stopper, when rotated in the neck, 

 makes a squeaking noise. 



Volatile oils are odorous principles, of the physical characteristics 

 of fixed oils, from which they differ by being soluble in alcohol and 

 by being volatile. To them is due the odor of plants. Volatile oils 

 are called essential oils from the fact that they possess, in a concen- 

 trated state, the properties of plants from which they are obtained. 

 They are mixtures of a number of substances and it so happens 

 in some cases that some of the substances are solids dissolved in the 

 liquid portion. These solids may sometimes be removed by chilling 

 the oil in a freezing mixture and draining off the unfrozen part (the 

 pleopten), leaving the solid part or stearopten. In other words 

 stearoptens are the solid portions of volatile oils. Examples: Cam- 

 phor, Menthol, Thymol. 



Saponins and Sapotoxins are neutral nonnitrogenous bodies 

 characterized by foaming with water, emulsifying fats, and laking 

 red blood cells. A few axe glucosides. The former term is given to 



