106 
ALOES. 
it make allowance for the circumstance that the quantities of heat calculated as being 
generated by the hydrogen, are calculated according to the heat-producing power of 
gaseous hydrogen. The results given above, as expressing the theoretical evaporative 
powers of these hydrocarbons, are therefore too high by an amount corresponding to the 
heat requisite to decompose the hydrocarbons and to convert the hydrogen from the 
liquid state it has in the hydrocarbons, to the gaseous state it has in the vapour result¬ 
ing from their combustion. 
The difference between the theoretical evaporative pow'er of hydrocarbons comprised 
within these limits of composition, and their evaporative efficacy will be determined by 
the relative proportions of carbon and hydrogen they contain, j ust in the same manner 
as shown already, so far as relates merely to the mode in which the heat generated is 
disposed of amongst the combustion products constituting the furnace gas resulting from 
their combustion. And it is here necessary to notice another circumstance of consider¬ 
able importance as regards the advantageous application of fuel, and especially hydro¬ 
carbon fuel. 
(To be continued.) 
ALOES. 
If we w r ere to inquire what drug is most frequently taken by the population of the 
British Isles, we believe the answer would be—aloes. Moreover, it is one of the oldest 
of drugs. The preparations in use at the present day and their names carry us back 
from the British Pharmacopoeia through the Middle Ages to the days of the Roman 
Empire. It is unique in its action. When properly used, it promotes an important 
function without disturbing others, and it is now what it was in the days of Celsus, the 
medicine par excellence for townsfolk and literary people —urbani and literarum cupidi 
—for those, in fact, w r ho oftenest send for a doctor, pay him best, and criticize him most 
sharply, who keep pill-boxes on their dressing-tables, who are miserable without their 
daily relief, and more miserable if it he accompanied with nausea, griping, or exhaustion. 
It may be worth while, then, to devote a few spare moments to the study of a drug so 
important. 
More than 2000 3 'ears ago aloes was as well known at Rome as it is now, and was 
spoken of in popular proverbs as the very symbol of bitterness. Yet the aloes, which 
was imported then, as now, from India and Arabia, though better than what was manu¬ 
factured on the shores of the Mediterranean, must have been of a very sorry descrip¬ 
tion. Not only was it largely adulterated with stones and sand, but it is clear, from 
the descriptions of Dioscorides and Galen, and the enormous doses in which it was given, 
that it possessed such a comparatively large proportion of the so-called resinous ingre¬ 
dient—that which is insoluble in water and is rejected in making the watery extract— 
that it had almost as great a reputation as an astringent and desiccative as an aperient.* 
It formed a part not only of aperient boluses and hierce pierce, but was an ingredient in 
those resinous applications to wounds and ulcers of which the old books contain legions, 
and of which the Friar’s Balsam, or tinct. benzoes co., containing aloes, is a venerable 
survivor, and the carbolic acid treatment a reproduction. In fact, Galen clearly recog¬ 
nized two elements in it—one moderately astringent, one vehemently bitter. To the 
former were ascribed its virtues as a tonic and vulnerary, to the latter as a purgative. 
They had a plan in those days of ivashing drugs. They found by experience that the 
oxide of copper and other coarse metallic preparations in vogue were deprived of much 
of their irritant property by dissolving out their soluble parts ; and in applying this to 
aloes, they discovered that, if w r ell washed, it lost its purgative virtue nearly or alto¬ 
gether,—a rough bit of analysis, but one which medical practitioners, down even to our 
own day, have hardly seen the force of, or they would not have talked as they did of 
the activity of the so-called resinous part of aloes. We find Dr. Garrod and Dr. Farre, 
according to the admirable lectures on the Pharmacopoeia by the former, published in 
this journal in 1864, making experiments, even then, to convince their weaker brethren 
of the worthlessness of the insoluble part of aloes. 
We may now skip about 1200 years, during which medical science was chiefly kept 
* Vide Galen, De Simplic. Rem., lib. vi. 
