The inner spongy substance of the leaves in a decayed state has been employed as tinder and the fibres may be spun into a strong, useful thread. The fleshy leaves of the true Aloe contain near the epidermis or outer skin, a row of fibrovascular bundles, the cells of which are much enlarged and filled with a yellow juice which exudes when the leaf is cut. When it is desired to collect the juice, the leaves are cut off close to the stem and so placed that the juice is drained off into tubs. This juice thus collected is concentrated either by spontaneous evaporation, or more generally by boiling until it becomes of the consistency of thick honey. On cooling, it is then poured into gourds, boxes, or other convenient receptacles, and solidifies.
Aloes require two or three years' standing before they yield their juice.
In the West Indian Aloe plantations they are set out in rows like cabbages and cutting takes place in March or April, but in Africa the drug is collected from the wild plants. The most important constituents of Aloes are the two Aloins, Barbaloin and Isobarbaloin, which constitute the so-called 'crystalline' Aloin, present in the drug at from 1O to 30 per cent. Other constituents are amorphous Aloin, resin and Aloe-emodin. The proportion in which the Aloins are present in the respective Aloes is not accurately known. The manner in which the evaporation is conducted has a marked effect on the appearance of the Aloes, slow and moderate concentration tending to induce crystallization of the Aloin, thus causing the drug to appear opaque.