198 VETERIi^ARY MATERIA MEDICA. 



at night by turpentine fumes. The flies are six to 

 ten lines in length, two to three lines broad, and 

 weigh one and one-half to two grains. The parts of 

 their greenish, bronze-like wings are discernible in 

 the powdered drug. Cantharides may be extracted 

 by maceration in alcohol, ether, acetic acid, fixed and 

 volatile oils. Its active principle — cantharidin — of 

 which it contains about two per cent., occurs as col- 

 orless scales or crystals, insoluble in H^O, but soluble 

 in alcohol, ether, acetic acid, chloroform, and oils. 

 The activity of Spanish fly is impaired by age. It 

 must be kept in well-stoppered bottles. 



Physiological Actions.— Cantharides is a pow- 

 erful irritant, and produces its effect upon any part 

 of the animal organism with which the free can- 

 tharidin is brought in contact. Externally applied 

 it stimulates and vesicates, and is used as a coun- 

 ter-irritant. Taken internally it irritates the diges- 

 tive mucous membranes, large doses producing vio- 

 lent gastro-enteritis, strangury, and heematuria. 



Cantharides produce redness, vesication, and 

 sloughing of the skin or mucous surfaces, in accord- 

 ance to the strength of the preparation used and 

 the length of time it is left on. The usual " canthar- 

 ides blister," vesicates in from four to t^velve hours; 

 the vesicles soon burst and discharge a yellowish ser- 

 ous fluid, which must be carefully w^iped away, as 

 in many instances this also will vesicate. The sur- 

 rounding parts should always, therefore, be protected 

 by the use of lard, vaseline, etc. Cantharides is given 

 internally in chronic c^^stitis and to prevent the invol- 



