ON THERAPEUTICS. 
697 
testinal membrane, and increase their secretion at the same 
time. This agent is by some practitioners not considered 
safe for the ox. We can only assert, that we have employed 
it, both in the same doses and for the same objects, as those 
dictating its use in the treatment of the horse, and cannot 
recollect any symptoms induced by it that would lead us to 
condemn it. As a cathartic, however, it is seldom given 
alone ; when it is necessary to augment the biliary secretion, 
then it is most valuable, and the laxative effect that follows is 
seldom objectionable, although it requires careful watching, 
as there appears to be a remarkable susceptibility on the part 
of the mucous membrane under the influence of this drug, 
and fatal superpurgation is very common from exposure 
to cold or wet, after the exhibition of repeated doses of it. 
The various oleaginous purgatives produce their effects 
either mechanically or by the operation of a medicinal prin¬ 
ciple they contain, as instanced in linseed and castor oils. 
Excepting to such animals as dogs, calves, and occasionally 
to sheep, we have long discontinued the use of oils as cathar¬ 
tics, merely on the ground that no particular advantage 
attends their use; while, as a rule, they are bulky and incon¬ 
venient to give. They are, however, to be recommended to 
the amateur in medicine on account of their safety, as super¬ 
purgation of a serious character seldom or never attends even 
their excessive use. 
Clysters may contain a purgative agent, and which may 
thus be brought in contact with the intestinal surface; or in 
the simple form of warm water they distend the rectum , and 
thus induce contraction , besides softening the feculent matter, 
and so promoting its expulsion ; while from their cleansing 
influence upon the mucous surface, they may even tend to 
produce an increased secretion from it. 
Mashes owe their action to minute particles of silica, which 
probably increase the secretion by slightly irritating the 
lining membrane. 
The sulphates of magnesia and soda are considered 
to operate by endosmose and exosmose, and the same action 
would belong to all saline purgatives. Their effects are some¬ 
times very quickly developed, and no irritation seems to 
follow their use. For cattle, the sulphate of magnesia is the 
ordinary purgative. Still there is no reason for our confining 
its employment to the ruminant. We have used it with 
beneficial effect for all our patients, horses being equally 
with the ox susceptible to its action. Where saline purga¬ 
tives are indicated, the salt may be given in doses of from 
