188 MEDICINAL PLANTS. 



Acidulous water 5.5 



Thick brown oil 24.5 



Thin empyreumatic oil 29.0 



Charcoal * 30.5 



Gases consisting of carbonic acid and carbureted 



hydrogen 10.5 



100.0 



Hence it is inferred that guaiacum agrees in many respects with 

 the resins, but it differs from fhem, 1. in the quantity of char- 

 coal it leaves when distilled in close vessels ; 2. in the action that 

 nitric acid has upon it; and, 3. in the changes of colour that it 

 undergoes when its solutions are treated with nitric and oxymuriated 

 acids. Its properties may be thus enumerated : it is a solid sub- 

 stance resembling a resin; its colour varies, but is generally green- 

 ish ; it is readily dissolved in alcohol ; alkaline solutions dissolve it 

 with ease ; most of the acids act upon it with considerable energy ; 

 if digested in water, a portion is dissolved, the water acquiring a 

 greenish-brown colour; the liquid being evaporated, leaves a brown 

 substance which possesses the properties of an extract, being soluble 

 in hot water and alcohol, but scarcely at all in sulphuric ether, and 

 forming precipitates with the muriates of alumina, tin, and silver. 

 [Linn. Woodv. Lewis. Pantologia. Phil. Trans. 



section xix. 



Scammony. Jalap. 

 Convolvulus Scammonia. Convolvulus Jalapa. Woodv. 



The genus Convolvulus or Bind-wind is very extensive and 

 embraces not less than a hundred and twenty species distributed 

 over the different quarters of the globe. Of these several are medi- 

 cinal : but the chief are the two enumerated in the title to this 

 section. 



1. C. Scammonia. Scammony Bind-weed. This plant grow s 

 plentifully about Maraash, Antioch, Ecllib, and towards Tripoli in 

 Syria: it was first cultivated in England by Mr. Gerard, in 159/. 

 The root is from three to four feet long, and from nine to twelve 

 inches in circumference, covered with bark of a light grey colour ; 



