METHODS OF PRODUCING IRRITATION 333 



sorbed, leaving an empty sac under the skin. If still greater action 

 is secured, the first two steps will be repeated, but these will be fol- 

 lowed by small pustules. The reason for the distant separate pus- 

 tules instead of a diffuse inflammation is based upon the theory that 

 the agent is unable to pass through the horny layer of the skin but 

 can pass in and irritate the orilices of the glands. The local ef- 

 fects produced from irritants are exactly similar to other forms of 

 inflammation, pain, swelling, redness, etc. 



Remote Action. Certain changes in the entire organism always 

 accompany local irritation. These are due to stimulation of various 

 centers in the medulla and are generally believed to account for any 

 benefit from counterirritation. The centers particularly involved are 

 those regulating the heart, vasomotor and respiratory. A moderate 

 degree of irritation accelerates the heart, through some unknown 

 manner, while stronger irritation slows the heart through stimula- 

 tion of the vagus center. Blood pressure is raised by moderate stim- 

 ulation but on account of the decreased rate of the heart is lowered 

 by sharp irritation. The increase in blood pressure is probably due 

 to stimulation of the vasomotor center which constricts the blood 

 vessels over wide areas. This constriction is not general but is more 

 pronounced in the abdominal vessels, less so in the limbs and skin. 

 The respirations are stimulated by mild irritation but depressed by 

 stronger ones. 



Methods of Producing Irritation and Counterirritation. 



1. Bacterial. 



2. Friction and massage. 



3. Acupuncture. 



4. Scarification. 



5. Temperature. 



6. Cupping, venesection and leeches, 



7. Electricity. 



8. Drugs. 



1. Bacterial. This method was widely used in the early days of 

 medicine but is now obsolete. It consisted in using setons or rowels, 

 which were pieces of gauze or other fibrous material, pushed under 

 the skin and allowed to suppurate. Occasionally a piece of some 

 vegetable was placed beneath the skin to act as a foreign body and 

 cause suppuration. 



2. Friction and massage. Here the benefit is due partly to the 

 friction produced and partly to the massage of the parts. The bene- 



. fit obtained from the use of liniments is partly due to the friction 

 produced during their application. 



3. Acupuncture. This consists of thrusting fine needles deeply 

 into the tissues. It causes considerable inflammation and is said to 



