276 ON ALOIN, THE CATHARTIC PRINCIPLE OF THE ALOES. 
sented the appearance of an opaque straw-yellow mass, breaking 
short and of a dull fradture. Its taste was intensely bitter, and 
distinctly aloetic, but entirely without smell. It was found to 
be quite combustible, and to leave no ash on being burned on 
platinum foil. Its solution acted on test paper neither as an 
acid nor an alkali ; it was, therefore, a neutral body. It dis- 
solved in very small quantity in cold water — not above a grain 
to the ounce — but very readily when heated. It is very soluble 
in acetic ether, and also in acetic acid, of about twenty-five per 
cent., even in the cold; four grains may be easily dissolved in 
a fluid drachm of either of these liquids. In lime water it is 
considerably more soluble than it is in cold distilled water. Oil 
of turpentine and chloroform do not appear to have any solvent 
action on it. It is very readily dissolved by aqua potassae, and 
other alkaline liquids. In rectified spirit, with the assistance of 
heat, it dissolves in large quantity ; and on very slowly cooling, 
out of contact with the air, it crystallizes in beautiful yellow 
satiny tufts of rhombic plates. The spirituous solution, how- 
ever, refuses to give crystals unless above forty grains to the 
fluid ounce of spirit be used. It is, therefore, very soluble in 
this menstruum — twelve parts by measure being capable of 
holding one part in solution. Weak spirit is also a good 
solvent ; for on adding water to a strong alcoholic tincture, there 
is no separation. Sulphuric ether dissolves it very sparingly. 
From a consideration of all these characters, we became satis- 
fied that the substance which had been separated by us from 
the commercial Barbadoes aloes had never been made known 
before, and therefore was a new substance ; but whether the 
interest attached to it should terminate here remained to be 
seen. Of course, the first and most important question which 
suggested itself to the mind, and which remained to be solved, 
was — Whether the crystalline substance, which we had now 
convinced ourselves was an educt, and not a product, from the 
aloes, had any of the virtues of aloes as a medicine, or whether 
the virtues of aloes were concentrated in it, and depended on its 
presence for their action on the living body. 
The first trial, with the view of ascertaining its action on the 
body, was made with half a grain, and it acted twelve hours 
after being taken, in the manner that so characteristically dis- 
tinguishes the action of aloes. The same quantity was again 
given to two healthy young men, with a similar result, except 
that in one about twenty-four hours elapsed before its operation. 
In the next two cases, one grain failed to act ; but in one of 
these, the dose having been increased to two grains, a very 
strong operation was the consequence. In a case where four 
grains were given, the person, a patient of Dr. Robertson, phy- 
