LOCAL ANAESTHESIA. 67 



frequently employed is hydrochloride of cocaine of i to 10 per cent, 

 strength. The addition of a trifling amount of bichloride of mercury 

 insures the solution keeping. Reclus recommends the following formula : 



Hydrochloride of cocaine . . . .1^ grains. 



Sublimate ...... -03 grain. 



Distilled water . . . . . • 2-i- fluid drachms. 



A few drops of this solution placed between the eyelids render the 

 superficial layers of the cornea insensitive in three minutes. 



By repeating the application at two-minute intervals the cornea, the 

 conjunctiva, and eyelids are often completely insensitive in less than ten 

 minutes, and anaesthesia lasts a quarter of an hour. The pupil dilates, 

 but as a rule the iris is not rendered insensitive unless the injection is 

 made into the anterior chamber. By this method puncture of the 

 cornea and removal of foreign bodies fixed in the conjunctiva are 

 rendered easy. Five or six subconjunctival injections made around 

 the ball of the eye permit the eye itself to be removed without great 

 pain. Cocaine acts equally well on other mucous surfaces, and under 

 certain conditions may be useful in painful inflammations of these 

 membranes. The most recent experiments appear to show, however, 

 that the blanching and anaesthesia are followed by congestion of the 

 parts, and the use of cocaine in gargles, etc., for inflamed pharynx has 

 been abandoned in human surgery, the after effects being bad. 



By a series of small injections along the course of a proposed in- 

 cision operation is rendered painless, provided the seat of operation be 

 in a mucous membrane or in the skin. A Pravaz's syringe fitted with a 

 long fine needle is used, the needle being inserted into the subcutaneous 

 connective tissue, or, better, into the thickness of the epidermis, follow- 

 ing the direction of incision. As the needle is gradually withdrawn 

 the piston is slowly pressed home, leaving the track filled with fluid. 

 The anaesthetic qualities of cocaine are increased by previously injecting 

 morphine. 



Arloing states that cocaine has no effect on the nerve-cells, its 

 action being confined solely to the terminal fibres of sensory nerves. 



Its toxicity varies according to species. In the dog the dose varies 

 from f to i^ grains. Strong solutions offer no advantages and are 

 dangerous. Cocaine solutions of whatever strength, lose, more or less 

 completely, their anaesthetic quality on becoming acid, but this can be 

 restored by neutralising the liquid. 



Local Anaesthesia by Infiltration. — Dr. Schleich produces 

 local anaesthesia by causing artificial oedema in the region of opera- 

 tion. He performed amputation and even laparotomy successfully. 



