Besides quinine, which stands at the head of the list, and the action of which has been already explained, there is salicine, whose action in reducing temperature is very marked, though the modus operandi is not yet clearly defined.
A number of synthetical compounds of German origin much in vogue in human practice are employed by some veterinarians, but their utility in equine practice cannot be said to have been established. The large doses required, and the considerable cost, preclude their use on a large scale in establishments where their therapeutical value could be best tested. Among them may be named antipyrin, antifebrin, kairin, phenacetin, etc.
The veterinarian is accustomed to regard saline aperients as "cooling " medicines, and they undoubtedly do reduce temperature in an indirect manner (see Aperients). Remedies which act upon the skin and kidneys also lower the animal heat, and the application of cold water does so by evaporation and the subsequent determination of blood to the surface. Clothing, by inducing perspiration and increased activity of the skin, also tends to lower the general temperature.
There are other drugs which depress the activity of tissues, and provided the loss by waste remains the same, a lowering of temperature follows. To this class belong alcohol and digitalis, strophanthus, aconite, and belladonna.
These drugs in proper doses do not reduce the normal temperature of the healthy animal, but there is general agreement among practitioners as to their effect in cases of pyrexia.
Quinine, as most of our readers are aware, is obtained from the bark of the cinchona tree (fig. 427). There are several varieties, some of which are richer in the alkaloids than others. The virtues of the bark were more or less known to the South American Indians before the Jesuits introduced it to Europe.