2. On account of capillarity, the surface is always cupped, 

 forming a meniscus. The reading should always be taken at the 

 lowest level of the meniscus. 



Chapter III. 

 SOURCE AND COMPOSITION OF DRUGS 



Drugs are obtained from both organic and inorganic substances. 

 The vegetable and biological preparations are obtained from the 

 former, while the various metals and their salts, the composition of 

 which is shown by their name and chemical formula, are obtained 

 from the inorganic. The greater number, probably are derived 

 from the vegetable kingdom or from plants. All the different 

 parts of a plant may be used in medicine but the active principle 

 to which their action is due is usually found more abundantly in 

 certain parts than others. In such cases the part or parts contain- 

 ing the largest amounts are used. The active principle may how- 

 ever, be quite evenly diffused throughout, in which case the entire 

 plant may be used. 



Gross Anatomy of Plants 



Underground Portions: These include the root, rhizome, 

 tuber, inlh and corm. The root is that portion usually without 

 chlorophyll and which does not have power to produce leaves. They 

 sometimes possess a bark which is used separately, (Sassafras). 

 Rhizomes are the underground portions capable of producing 

 leaves, (Hydrastis). A tuber is a portion of the root greatly 

 thickened which serves for the accumulation of reserve food ma- 

 terials (Aconite). A bulb is an increase in size of- the root leaves, 

 (onion, squill) ; while a corm is the thickened lowest part of the 

 stem (Colchicum). 



Portions Above Ground: If the entire plant above ground 

 is used, it is termed herb {herba or species) and consists of the 

 leaves, stems, and sometimes of the flowers and fruit. 



Stem. In herby plants it is termed stipes, in larger it is trans- 

 formed into wood (lignum) and covered with a bark (Cortex). 

 The leaves (folia) consists of a leaf stem (petiolus) and blade (la- 

 mina). There are also the flowers (flores), and fruit (fructus) or 



