VETERINARY MATERIA MEDICA. 645 



name nitrate of potash. It is the most useful, powerful 

 refrigerant : it greatly diminishes febrile action, and 

 determines its depleting action more certainly to the 

 kidneys than any of the saline articles we use. It is also 

 antiseptic and diaphoretic, and therefore of great con- 

 sequence in active fever, given two or three times a day, 

 in doses of three or four drachms. As an alterative it 

 is also well known ; but it is not a good plan, as practised 

 by some grooms, to infuse it into the water which horses 

 are to drink ; it is apt to disgust them with all liquids. 

 Nitre is sometimes used as a cooling lotion for inflam- 

 matory swellings arising from sprains. 



Nitre, Sweet SjArit of {Spiritus cBtheris nitrici). — This 

 is a valuable preparation of nitre, inasmuch as it is a 

 refrigerant, and yet, in some measure, a cordial, from its 

 rethereal composition ; therefore it is a useful medicine 

 in the more advanced stages of fever, in doses of four 

 ounces two or three times a day. It is also a useful 

 article to give in the immediate approach of the first 

 cold tit of fever, in a dose of two ounces. 



Nitrous Acid {Acidum nitrosum dilutum), or aquafortis, — 

 See Caustics. 



Oak Bark. — See Barks. 



Oils. — These are either fixed or volatile. The fixed oils 

 are so called because they are not liable to be changed 

 into vapour under any high degree of temperature, and 

 are also generally gained in quantities by expression. 

 The volatile oils, on the contrary, are produced by distil- 

 lation, and evaporate by a moderate heat. The fixed 

 kind, in horse practice, are, — 



Oil of Bay, an expressed oil from bay berries : now 

 obsolete, except in the recipes of the country smith. 



Oil of Castor. — See Castor Oil. — In very large doses 

 this occasions some disturbance in the bowels, and does 

 not often operate as a laxative ; but in doses of eight or 

 ten ounces, repeated every five or six hours, it proves 

 frequently an excellent laxative w4ien more drastic matters 

 are inadmissible. It is apt to be decried, and numerous 

 experiments are detailed to prove that it is noxious as 

 well as inert ; but hardly any two experiments agree. 



