ACTIONS AND USES 439 



for a few minutes, aloes softens and becomes adhesive. 

 At a low red-heat it is partially fused, froths up, chars, and 

 burns. Temperatures exceeding 150 Fahr. alter its com- 

 position and impair its purgative property. Moistened 

 with rectified spirit, a thin stratum, examined under the 

 microscope, exhibits numerous crystals. It is almost 

 entirely soluble in boiling water, which deposits, however, 

 as it cools, 60 to 80 per cent, of a brown resin. Good 

 specimens are almost entirely soluble in alcohol (40 to 60 

 per cent.). The watery solution, when cold, reddens 

 litmus, is deepened in colour by alkalies, blackened by 

 ferric chloride, and yields a yellow-grey precipitate with 

 lead acetate. 



COMPOSITION. Aloes contains from 25 to 30 per cent, 

 of an active yellow, crystalline, neutral bitter principle 

 aloin, which is noticed more in detail at the end of this 

 article ; and about the same proportion of an equally 

 soluble, uncrystallisable aloin, into which the crystallisable 

 form is convertible by heat ; and a pale-yellow, mobile, 

 mint-flavoured volatile oil, of which only an ounce is ob- 

 tained from 400 Ibs. of aloes. Besides mineral matters and 

 albumin, aloes contains about 30 per cent, of a transparent 

 brown resin, almost entirely soluble in rectified spirit, 

 occurring in large amount in inferior samples, in which it 

 is formed at the expense of the aloin, usually by exposure 

 of the juice to high temperatures during inspissation. 



ACTIONS AND USES. Aloes is purgative, and belongs to 

 the anthracene group ; a bitter tonic in small doses, in- 

 sufficient to increase the action of the bowels. 



GENERAL ACTIONS. Given by the mouth, it is dissolved in 

 the gastric fluid, and emulsified and saponified by the bile 

 and pancreatic juice. The presence of bile greatly assists 

 its action, and aloes given in enema is inactive unless bile 

 is injected with it, or the aloes is dissolved in glycerin, 

 which takes the place of the bile. Joseph Gamgee made 

 seven drachms of Cape aloes into a ball with sixty minims of 

 glycerin, rolled it in tissue paper and gave it to a horse, 

 which, in thirty- three minutes, was killed by dividing the 

 carotid artery. An hour later the ball was found entirely 

 dissolved ; the distinct odour of aloes in the stomach and 



