420 BIOLOGY AND HUMAN LIFE 



Animal sources of fuel are less common today than they were 

 formerly, when whale oil was burned to some extent under 

 * special conditions, both for heat and for light. 



311. Contributions to health. Plants and animals furnish 

 many substances of direct and indirect value in maintaining our 

 health and efficiency. On the side of keeping clean we have, 

 first of all, soap, which is made by treating plant or animal fats 

 with alkali solutions. Brushes, sponges, wash cloths, and simi- 

 lar aids to cleanliness all represent the use of plant and animal 

 material as contributions to health. 



The greater part of our drugs consist of plant products. 

 The exceptions are (i) a very few mineral products that are 

 used in the pharmacopoeia (see page 400), such as acids and 

 alkalis and a number of salts, and (2) the synthetic and coal- 

 tar products developed by modern chemistry. A very few are 

 derived from animals. Gummy or jellylike substances are ob- 

 tained from seaweeds (algae) and lichens, as well as from seed- 

 bearing plants. Among the latter, gums are obtained from 

 seeds, stems, and roots. Camphors and resins, as well as a great 

 variety of oils and essences, all derived from plants, are used as 

 flavoring agents, as irritants, and as antiseptics. Compounds 

 related to tannin are obtained from rhubarb, witch hazel, and 

 other plants for their astringent, or puckering, properties. The 

 drug ergot is obtained from rye that has been attacked by a 

 parasitic fungus. 



The most powerful drugs, the alkaloids, are obtained from plants ; 

 and until recently, when synthetic chemistry attacked this problem, we 

 had no substitutes for them. These organic substances, which are ''like 

 alkalis " in that they can combine with acids, are all more or less violent 

 poisons. Each produces some distinct effect upon protoplasm, so that 

 they have been very useful in dealing with special types of situations. 

 For example, morphin, derived from the juice of the poppy fruit, dulls 

 the senses or actually puts one to sleep, while leaving the imagination 

 unrestrained by actual facts or consistent thinking. Cocain, obtained 

 from the leaves of the South American coca plant, ^ produces insensi- 



^This is not to be confused with the coco palm, from which we get the 

 coconut, or with the cacao plant, from which we get chocolate and cocoa. 



