THE PAGE OF NATURE. 107 



medical history, lichens formed the principal drugs in 

 the pharmacopoeia, and were prescribed for almost all 

 the ills that flesh is heir to. Superstition had much to 

 do with their popularity in this respect. Their strange 

 shapes, their anomalous character, occupying, as it were, 

 an intermediate position between plants and minerals, 

 between life and death ; leading a perpetual mesmerized 

 or suspended existence ; the curious situations in which 

 they were found, growing on decaying wood or moist 

 earth, or on the bare rock in weird, lonely spots, where 

 fairies might sport and enchanters weave their unhal- 

 lowed spells; they were naturally enough supposed by 

 a credulous and ignorant people to be invested with 

 magic qualities. As the knowledge of plants became 

 more generally diffused, they lost much of their mystery, 

 and consequently of their power over disease; and now 

 they have almost entirely disappeared from medical prac- 

 tice. It must not be supposed, however, that they were thus 

 summarily expelled from the schools of medicine, because 

 they were entirely destitute of healing qualities. Some 

 of them have been found, by chemical analysis, to contain 

 principles of great efficacy in certain complaints ; but as 

 these principles varied in their strength, according to the 

 circumstances in which the plants were produced, no de- 

 pendence could be placed upon the action of the doses 

 administered. It is obvious that the chemical qualities of 

 cellular plants, whose construction is so extremely simple, 

 must vary considerably in different individuals and in 

 different situations. The nature of the matrix on which 

 lichens grow, and of the medium which surrounds them, 

 must, to a great extent, determine the presence in them 



