146 GENERAL THERAPEUTICS FOR VETERINARIANS 



6. Fats, oils, paraffin ointment, petrolatum, lanolin (adeps 

 lanae hydrosus). Protective, indifferent substances, replacing the 

 cutaneous fat, in acute eczemas; exert a disintegrating action in 

 chronic skin exudates. Pastes (zinc, starch, petrolatum), gly- 

 cerin gelatin (zinc gelatin), plasters (lead plaster, saUcylic soap 

 plaster) and varnishes are similar in action. 



7. Arseni trioxidum. Arsenic. Used internally as an alter- 

 ative in the form of liquor potassii arsenitis (5 to 10 drops for dogs; 

 5-10, 3i to ijss, for horses). More modem arsenical preparations 

 are salvarsan and atoxyl. 



2. CUTANEOUS IRRITANTS. ACRICS 



Synonyms: Derivants, epispastics, rubefacients, vesicants, pustulants, 

 suppuratives, irritants, erethistics, dermerethistics; acrid, stimulating, irri- 

 tating, derivative medicines; digestive medicines in a surgical sense; blisters. 



Actions. — The term aeries is used to designate those drugs 

 which act as irritants to the skin and mucous membranes and to all 

 organs in general which contain nerves and blood-vessels, produc- 

 ing hypersesthesia and pain together with hyperaemia and inflam- 

 mation. In the restricted sense the term includes only the cuta- 

 neous irritants. The effects resulting from the action of the aeries 

 correspond exactly to the changes produced in the skin by other 

 causes of inflammation (traumatic, thermic and infectious irri- 

 tants). Numerous investigations concerning the production of 

 inflammation by aeries have been made since those of Cohnheim, 

 among which the work of Leber is especially worthy of considera- 

 tion. In the purely aseptic inflammation, produced by cantharides 

 or croton oil and not by bacteria, the following changes are to be 

 observed: First, the vessels are dilated reflexly, producing hyper- 

 semia, redness, swelling and increased temperature in the affected 

 part of the skin or mucous membrane. Then follows an exudation 

 of plasma (serum) from the blood. Soon after this there is an 

 emigration of leucocytes through the cement substance of the endo- 

 thelium. The principal cause of this emigration is not the amoe- 

 boid movement of the leucocytes, the increased blood-pressure nor 



