ON ALOIN, THE CATHARTIC PRINCIPLE OF THE ALOES. 277 
sician to the Edinburgh Royal Infirmary, had been getting one- 
quarter grain doses of elaterium with little effect. The opera- 
tion in this case was rather violent. In numerous other cases 
in which it was tried, it invariably operated in doses of from 
one to two grains. The result of these trials was the removal 
from our minds of every doubt of the crystalline body yielded 
by the aloes being that on which its cathartic action depended, 
being, in fact, the active principle of the drug. 
To the new crystalline substance we have given the name of 
aloin. It was obtained, as already stated, from Rarbadoes aloes; 
and it became a question, both interesting and important, to 
ascertain whether it could be procured from other kinds, such as 
the Socotrine and Cape. With this view, we, therefore, put 
these two kinds of aloes under treatment, operating in the very 
same way as with the Barbadoes, but without success. That 
the aloin is present in both of these sorts there cannot be a 
doubt. In fact, we have no hesitation in stating our belief, that 
we shall yet obtain it from these, the result of what little we 
have done convincing us of its existence in them as well as in 
the Barbadoes sort, but by the presence of impurities, chiefly, 
we suspect, of a resinous nature, the aloin is probably so en- 
tangled that it cannot get freedom for that arrangement which 
seems necessary for ready crystallisation. That a crystalline 
body may be present, and yet may not crystallise, will, we be- 
lieve, be readily admitted by any one much occupied with the 
process of crystallisation. Another cause may perhaps be found 
in changes and decomposition, originating in faulty processes of 
preparation, the result of ignorance, carelessness, or fraud. That 
faulty methods of preparing the aloes may be one cause of cer- 
tain kinds of the drug not giving aloin, is rendered probable by 
the following circumstance which came under our observation. 
If aloin be crystallised, either from water or rectified spirit, and 
the crystals left in contact with the mother liquid, in the course 
of a few weeks, but more quickly in the latter than in the former 
case, the crystals will have then entirely disappeared, thus 
shewing the readiness with which the aloin loses its crystallis- 
able character. Keeping these considerations in view, and 
taking advantage of what little we now knew of the properties 
of the aloin, the following steps were taken : — 
The watery solution of Cape aloes having been mixed with 
a very little sulphuric acid, to separate a quantity of colouring 
matter along with a fatty acid and chlorophyle, was filtered and 
then evaporated in vacuo to a thin extract. The extract was 
shaken with a quantity of ether, which was then poured off, and 
allowed to evaporate very slowly. Aloin at length crystallised, 
but, of course, from its slight solubility in ether, the quantity 
