MATERIA MEDICA. 
167 
immediate effect on the membrane of the intestines being stimu¬ 
lating rather than depressing, they quicken the peristaltic motion of 
the bowels without increasing the intestinal secretions, yet there is 
no marked activity of the absorbent system, and no decided phe¬ 
nomena 6f revlusion : thus the laxatives are principally employed 
as simple evacuants, and under that title they are infinitely pre¬ 
ferable to the drastic purgatives in any disease attended by con¬ 
siderable inflammation, the intensity of which may be increased 
by the irritation of the physic. 
Purgatives drawn from the Mineral Kingdom. 
Sulphate of Soda. —This salt is a mild purgative, and of 
frequent use in veterinary practice on account of its little price 
and the convenient form under which it may be administered. 
To cattle it is given alone, or combined with vegetable purga¬ 
tives, in doses of from four to twelve ounces. 
It has been recommended in very small doses for chronic 
diseases of the skin: for it has been imagined that, by giving 
new activity to the exhaling vessels of the mucous membrane of 
the intestines, and to the urinary apparatus, it may produce a 
kind of salutary revulsion. It has, however, no especial influ¬ 
ence on the capillary system generally. 
Sulphate of Potash. —This substance possesses nearly the 
same properties as the preceding, but it is seldom employed, be¬ 
cause it is dearer; and, on account of its more sparing solubility, 
it cannot be so conveniently administered. 
Sulphate of Magnesia. —This differs little in medicinal 
effect from the sulphate of soda, except that the latter acts more 
decidedly on the urinary organs. It is given in the same doses, 
and in the same manner. 
Magnesia. —Administered in doses of six or eight ounces, 
this is a mild purgative, but it is rarely employed for this purpose 
by veterinarians. It is ordinarily given to neutralise any acid 
that may be suspected to exist in the stomach or intestines : on 
this account it is useful in tympanitis and diarrhoea. The dose 
for the horse and the ox varies from three drachms to three 
ounces; to the colt and the calf it is given in doses of two 
drachms, either incorporated with honey, or suspended in some 
mucilage. 
__ O ^ 
tartrate of Potash. —This is a very mild purgative, but 
as it is somewhat dearer than the bi-tartrate, it is seldom 
used. 
Bi -tartrate of Potash (Cream of Tartar).— Adminis¬ 
tered in small doses (two ounces), it acts as a cooling medicine, 
and a diuretic; in triple or quadruple doses it is a mild purga- 
