ALOES 433 



exhibits when examined under the microscope minute prismatic 

 crystals embedded in a transparent resinous mass. Such an aloes 

 is termed ' hepatic ' or ' livery.' The crystals that it contains are 

 aloin, and the reason why in this case the aloin crystallises, whilst in 

 the vitreous aloes it does not, is probably to be found partly in the 

 fact that the conditions under which evaporation takes place are more 

 favourable to crystallisation, and partly in the conversion of the 

 crystalline aloinin to an amorphous modification (see below). Never- 

 theless every variety of aloes not only may, but actually does, occur 

 in both the vitreous and the opaque modification. 



Varieties of Aloes. -The chief commercial varieties of aloes may 

 be conveniently considered under three heads, viz. : East African, 

 South African, and West Indian. 



EAST AFRICAN ALOES 



1. Socotrine Aloes. This variety is stated in the British 

 Pharmacopoeia to be derived from Aloe Perryi, Baker, and probably 

 other species. It is brought by Arab traders from the east coast of 

 Africa, the island of Socotra (600 miles west of Aden), and possibly 

 also from the coast of Arabia, to Bombay, whence it is exported to 

 Europe. It arrives usually in kegs or tins, or occasionally in large 

 barrels, and commonly has a pasty, semi-liquid, or even treacly 

 consistence. It is then of a brownish yellow colour and quite opaque, 

 but if not too viscid it separates on standing into a clear, dark brown, 

 supernatant liquid and a dark yellow sediment which, under the 

 microscope, is seen to consist of minute, prismatic crystals (aloin). 

 The odour of the fresh aloes is usually remarkably urpleasant, but this 

 may change when the aloes is kept under certain (not at present 

 precisely known) conditions to a rather agreeable fragrance that has 

 been compared to myrrh and saffron. 



As this variety of aloes contains a varying amount of water, and 

 is not, as imported, in a suitable condition for use in pharmacy, it 

 must be dried at a gentle heat, best by exposing it on wooden trays 

 in a warm room. It then forms hard, dark brown or sometimes, if 

 dried at too high a temperature, nearly black masses, breaking with 

 a dull, waxy, uneven, often porous fracture, and possessing a strong, 

 characteristic unpleasant odour and an extremely bitter, nauseous 

 taste. It should be almost entirely soluble in alcohol, and yield about 

 half its weight to cold water. Small splinters are opaque, but 

 mounted in a drop of almond oil and examined under the microscope 

 they exhibit numerous minute prismatic crystals (of aloin) embedded 

 in a transparent, dark yellowish brown mass. This aloes therefore 

 belongs to the class of aloes known as livery or hepatic aloes. From 

 other aloes it may be distinguished by moistening a little of the 



28 



