52 
PHARMACEUTICAL BOTANY 
centrated H2SO4, the cells containing strophanthin will assume a 
bright green color. 
6. Salicin. — Salicin is a glucoside occurring in the cell sap of the 
bark and leaves of the Willows and Poplars. Sections of these 
mounted in concentrated H2SO4 will show a red coloration in the 
cells containing this substance. If water be added a red powder is 
thrown down. 
7. Saponin, another glucoside, found in Soap Bark, Senega, 
Saponaria and other drugs also takes a red color with strong H2SO4. 
8. Coniferin is a glucoside, occurring in the cell sap of the spruce, 
pine, and other plants of the Coniferce. If sections containing it are 
first treated with a solution of phenol and then with sulphuric acid, 
the cells containing it take on a deep blue color. 
8. Digitoxin, a glucoside found in the leaves of Digitalis purpurea, 
is colored green with hydrochloric acid. 
The glucosides are very numerous. Those listed above represent 
but a few examples. They arise in the cell sap of plants containing 
them as products of constructive metabolism (anabolism) and are 
thought by many to have the function of protecting plants against 
the ravages of animals. Some are known to serve as reserve food. 
All glucosides are characterized by the property of being split up 
into glucose and other substances when acted upon by a ferment, 
dilute acids or alkalies. 
9. Alkaloids. — Chemically, these are basic carbonaceous amines 
which like glucosides are products of metabolism. Their method 
of formation in plants is uncertain. Some hold that they are kata- 
bolic products, resulting from the breaking down of tissues, while 
others believe them anabolic in character. They undoubtedly serve 
as defensive agents in plants containing them on account of their 
bitter taste and poisonous properties. 
Properties of Alkaloids 
Alkaloids are invariably found in combination with acids forming 
salts which dissolve in water or alcohol. They are composed of 
carbon, hydrogen and nitrogen. Some contain oxygen. They are 
precipitated from saline solutions by the addition of alkalies. They 
