t 



186 DEPRESSANTS TO PERIPHERAL NERVES 



limited extent, but the alkaloid cocaine is very extensively used as a 

 local anesthetic. 



External Action. Cocaine produces no action upon the un- 

 broken skin because the drug is not absorbed, but if it is mixed with 

 some substance which is absorbed, or is injected hypodermieally or 

 is in any way brought into contact with a nerve, it produces local 

 anesthesia by paralyzing the sensory nerves. The part soon becomes 

 pale on account of constriction of the bloodvessels. Very large 

 doses may also paralyze the motor nerves. Anesthesia takes place 

 in from five to ten minutes after its application and lasts for fifteen 

 to thirty minutes, but may be prolonged and intensified by the 

 addition of a small amount of adrenaline chloride solution, which 

 constricts the bloodvessels and delays the absorption of the cocaine. 



Anesthesia may be produced if the drug is applied to any part of 

 the nerve, from its ending to its posterior root : so anesthesia may be 

 obtained by : 



1. Application to mucous membranes. 



2. Injection beneath mucous membranes or skin. 



3. Injection into a nerve. 



4. Injection into the spinal canal which is known as spinal Anal- 

 gesia, or anesthesia. The motor nerves are not so readily affected. 



Spinal Analgesia. To obtain spinal analgesia in man % — Vi 

 grain of cocaine hydrochloride in aqueous solution is injected into the 

 spinal canal, the needle being inserted between the third and fourth 

 lumbar vertebrae. The toes and perineum become anesthetic in about 

 three to four minutes, and anesthesia rapidly ascends until it reaches 

 the umbilicus, the entire body below the injection being anesthetized. 

 Jonnesco has made the injections higher up in the cord, using a mix- 

 ture of stovaine and strychnine. Although his reports are excellent 

 the method has been abandoned in this country as unsafe. This 

 method of producing analgesia in veterinary medicine has been con- 

 fined to work upon the dog, but it has not gained much prominence. 



Digestive System, Taken per os, the gastric mucosa is numbed 

 and the sense of hunger lessened. Small doses are said to increase 

 and large doses decrease peristalsis. Those taking cocaine or coca 

 can go long periods and work for several days without food and 

 apparently seem to have no sensation of hunger. The drug is not a 

 food, however, as the body rapidly wastes. On account of its local 

 anesthetic action cocaine is frequently used to control or check nausea 

 and vomiting. Very large doses tend to paralyze the bowels and 

 cause constipation. 



Circulation. Probably cocaine has little direct effect upon the 

 circulatory system, but the vagus is somewhat depressed and the 

 pulse therefore quickened and more forceful. Large doses slow the 

 heart. The effects of the drug upon this system vary greatly with 



