524 
EFFECTS OF MERCURY ON HORSES. 
5. What symptoms may be expected to arise from inflam- 
mation of the membranes of the brain, proceeding from other 
cause than the bite of a mad dog, supposing that to be one 
cause of such a pathological condition ; and how are the others 
to be distinguished?] 
EFFECTS OF MERCURY ON HORSES. 
By Mr. W. Percivall. 
[Continued from page 444.] 
Hydrargyrum cum Creta, as every medical man knows, 
is a slate-coloured powder, the result of extreme mechanical 
division of the mercury amid the chalk, and, perhaps, of some 
partial oxydation of the former. It may be prescribed for horses 
in doses varying from a drachm to an ounce ; and will be found 
useful in disordered states of the alimentary canal, and of the 
biliary and pancreatic secretions. In diarrhoea, I have found it - 
very serviceable in restoring healthy action and secretion. In 
cases where the state of the stomach or bowels forbids the use of 
calomel, and yet mercury in some form appears desirable, this 
will be found a very proper medicine. As an alterative — when 
the animal is hide-bound and does not make flesh, and voids 
dung offensive in odour and unnatural in colour, and altogether 
assumes an unhealthy aspect, and is weakly with it — doses of 
hydrargyrum cum creta, alternated with aperient doses of aloes, 
are often attended with the happiest results. 
Hydra rgyri Chloridum — the calomelas of the London 
Pharmacopoeia for 1720 — is on various accounts the form of mer- 
cury usually administered both in human and veterinary prac- 
tice : indeed, in respect to the former, it has been truly said by 
Dr. Spillan, “ There is no article in the materia medica more 
frequently used, or more grossly abused, than calomel.” It 
may be regarded as, in general, a mild and safe form for the ex- 
hibition of mercury. The surgeon would not know what to do or 
where to seek a substitute, were he deprived of calomel : no 
bottle in his pharmacy is oftener called into requisition than that 
labelled “ hydrarg. sub-morias” or “ hydrarg. chloride The 
veterinary surgeon has never been without calomel among his 
medicaments — has had frequent recourse to it in his practice ; 
and yet, notwithstanding the great repute in which it is held 
among surgeons, to him — in his horse-practice at least — it ap- 
