56 General Principles of Veterinary Medicine, 



a further means of guarding against this, the fomented sur- 

 faces may have a light dressing of mustard rubbed into them. 



Ointments are prepared by mixing the drug to be used 

 with lard, butter, or cerate, or what is far better, the petro- 

 leum product called petroleum ointment, cosmoline or 

 vaseline. This substance never becomes rancid, has no 

 unpleasant odor, and by adding wax or parafine can be 

 made of any desired thickness. Ointments are of especial 

 use in diseases of the skin and hair, though as their ingre- 

 dients can be absorbed by the skin, they are sometimes 

 employed to introduce medicines into the system. 



Plasters are solid adhesive substances usually containing 

 litharge, with resin, wax, soap, tar or pitch. They are not 

 very useful in veterinary practice, and when employed it is 

 usually in the form of charges. These are where the ingre- 

 dients of the plaster are melted or poured directly on the 

 skin. They are then covered with ravelled tow or lint, and 

 confined by a linen or leathern bandage. In former times 

 this was a popular practice with farriers, but has gone some- 

 what out of date. 



They are well adapted as a dressing to slow inflammations, 

 particular of the joints, ligaments, tendons or feet. They are 

 even more useful in joint affections in cattle than in horses, and 

 sometimes benefit such cases when other means have failed. 

 They are, however, often difficult to apply and keep upon 

 the part, and for this reason can generally be superseded by 

 water dressings, lotions and fomentations. 



WEIGHTS AXD MEASURES. 



The weights and measures used by veterinarians are the 

 apothecaries' weight and wine measure. 



