384 MATER i A MEDIC A AND THERAPEUTICS. 



Blisters are chiefly employed to control hyperaemia and 

 the inflammatory process ; to promote the absorption of 

 morbid products; to relieve pain; and to arrest spasm and 

 other reflex symptoms. The principle upon which they are 

 believed to act is discussed under Counter-irritants in Part III. 



Spanish fly is most frequently used in cerebral hyper- 

 aemia, being applied to the nape ; in acute pleurisy, 

 pericarditis, peritonitis, and meningitis sometimes in the 

 first stage, especially if pain be severe, but more frequently 

 in the third stage, to promote absorption of effusions and 

 exudations ; in subacute or chronic inflammation of the 

 viscera, such as pneumonia, when resolution is slow, or the 

 disease threatens to become chronic ; and in subacute or 

 chronic inflammation of peripheral parts, such as the con- 

 junctiva, joints, bones, etc. Neuralgia, if distinctly local 

 in origin and due to congestion or inflammation of the 

 nerves, is sometimes completely relieved by cantharides 

 blisters ; and the pains of acute rheumatism are undoubtedly 

 dispelled by the same means, which is further believed by 

 some physicians to cut short the whole rheumatic process. A 

 blister on the epigastrium is a successful mode of treatment 

 in some forms of gastric pain and vomiting. 



In every instance, cantharis should be cautiously applied 

 to children, to persons suffering from kidney disease, and to 

 the aged and infirm. The back must not be blistered in bed- 

 ridden persons, lest bed-sores be produced. Blisters must 

 never be forgotten or left too long on the skin, otherwise 

 ulceration may be set up, as well as the remote local effects of 

 the drug to be presently described. 



Internally. Cantharis is an irritant to the mouth, throat, 

 and stomach, and must be given well diluted and in small doses 

 of the tincture only. 



2. ACTION IN THE BLOOD, AND SPECIFIC ACTION AND USES. 



Cantharidin enters the blood both from the blistered sur- 

 face and the stomach. The active principle finds its way into 

 all the organs, to which it clings rather tenaciously. In large 

 doses it disturbs the heart, respiration, and nervous system, 

 producing a rapid pulse, headache, sensory disturbances, 

 mental confusion, and finally death by asphyxia. It is not 

 used in this connection. 



3. REMOTE LOCAL ACTION AND USES. 



Cantharidin is slowly excreted by the kidneys, and ap- 

 pears in the urine, which conveys it to the bladder and genital 

 organs. Here it sets up a second set of local effects similar to 



