612 
INTRODUCTORY LECTURE. 
essentially they consist of one and the same substance, so 
that washed common chalk is the only agent of this class 
retained. It is singular that Layard, in his excavations at 
Nineveh found some of the first named of these sealed-earths ; 
thus proving them to be of very ancient usage. So, many 
alkaline salts obtained from different vegetables have given 
place to the carbonates of soda and potash ; chemistry having 
shown that one or the other of these is the available 
compound. 
Again, the use of oil of bricks, of earthworms, and 
swallows, has become obsolete ; with that of white, black, and 
green oils ; other and more consistent forms being sub- 
stituted. 
There can be no doubt, moreover , but that much good has arisen 
from the many experiments performed at this institution for 
the purpose of ascertaining the effects on the horse, and other 
animals, of most of the articles of the materia medica of the 
human practitioner. These led to the compounds of anti- 
mony, with one exception — the potassio-tartrate — being con- 
sidered of questionable utility, although they have long held a 
place in the estimation of the horseman. At any rate, their 
action is principally referable to a peculiar state of the 
system, over which we have but little control. I will, how- 
ever, now 7 only advert to those experiments by Professor 
Coleman on purgative agents, by which their number, so far 
as the veterinary surgeon is concerned, became at once con- 
siderably reduced, and certainty of operation secured ; 
he having ascertained that the more active and drastic 
purges to man, as scammony, colocynth, and gamboge, 
with rhubarb, senna, and jalap, w r ere to the horse ineffective 
as such, as they merely caused irritation without any corre- 
sponding action of the bow 7 els. 
Nevertheless, I am not quite satisfied but that through this 
some sacrifice has been made to the shrine of simplicity 
in prescribing ; and that we have lost sight of the advan- 
tages known to result from a judicious combination of 
medicinal substances, since scarcely any tw 7 o agents, even 
of the same class, produce their effects in precisely the same 
way: hence smaller doses of two, when combined, will 
operate more satisfactorily than much larger doses of one 
given alone. 
Here, without any controversy, is another proof of the 
good schools have accomplished ; for chemistry being taught 
in them, a knowledge of its laws is imperatively called for 
under this head, lest incompatible bodies should be mixed 
together, and a new 7 compound formed, whose influence 
