I 9 2 EIGHTEENTH CENTURY. PT. HI. 



spread of medical science as by the facts which he taught 

 them. 



But besides his influence upon medicine in general there 

 was one particular study which Boerhaave may be said to 

 have founded ; namely that of organic chemistry, or the 

 chemical analysis of substances occurring in plants and 

 animals. You will remember that the false science of 

 alchemy had always been much mixed up with chemistry, 

 and the alchemists had some strange mystical notions about 

 ' vital fluids,' which they supposed to exist in animals and 

 plants, and to cause their life and growth. Little by little, 

 however, more correct ideas had grown up in the sixteenth 

 and seventeenth centuries about the nature of life. Vesalius, 

 Harvey, Malpighi, Grew, and many others, had gradually des- 

 cribed more and more accurately the working of the different 

 organs of a living being, and now Boerhaave went farther, 

 and tried to discover by means of chemistry of what 

 materials these organs themselves are composed. 



In the same way that Geber had decomposed or divided 

 up inorganic substances, such as metals and earths, by distil- 

 lation and sublimation (see p. 43), so Boerhaave proposed to 

 decompose the organic structures of plants and animals, 

 and to discover the materials contained in them. To 

 accomplish this he took a plant, such as rosemary, and 

 putting fresh moist leaves of it into a furnace, heated them 

 gently and drove out all the moisture, which he collected 

 in a separate vessel. When this moisture had cooled down 

 into a liquid he examined it and found that it was made 

 up of water, and of different kinds of oils and essences, 

 according to the plant he had taken. For instance, from 

 rosemary he got an essence with the peculiar scent of 

 rosemary; from the bark of the cinnamon tree, Laurus 

 Camphorum, or Cinnamomum camphorum, he got essence of 



