62 LOCAL ANESTHESIA BY INFILTRATION. 



Podkopajeu and Negri, who recommend them for their simplicity, 

 harmlessness, and cheapness. 



The condition lasts, however, for not longer than twenty minutes. 

 Schleich's experiments showed that the best results attended the 

 use of a combination of cocaine, sodium chloride, and morphine. 

 He recommends the following formulae for use in man : 



/Hydrochloride of cocaine .... 0*20 



. . ! Hydrochloride of morphine .... 0-02 



Strong solution iChlorideofsodilim Q . 20 



IWater 100 



7 fluid drachms injected at each operation. 



/Hydrochloride of cocaine . . 0*10 



_., , , , ' Hydrochloride of morphine . . 0-02 



Moderately strong solution - CMoride of godium _ _ _ . 20 



( Distilled water .... 100 

 14 fluid drachms injected at each operation. 



/Hydrochloride of cocaine . . . . 0-o| 



.., . . ,. Hydrochloride of morphine .... 0'005 

 Weak solution jC h lorideof sodium .2o 



(Distilled water 100 



Use up to 140 fluid drachms at each operation. 



He renders even the first prick of the needle painless by previously 

 spraying the point of puncture with a mixture of four parts of 

 sulphuric ether and one part of petroleum ether. Mucous membranes 

 are rendered insensitive by dabbing with 10 per cent, carbolic solution, 

 or with a solution of cocaine. The needle is slowly introduced into 

 the skin itself in a direction parallel with the surface, and must not 

 enter the subcutaneous tissue. As soon as the point has travelled a 

 quarter to half an inch beyond the primary puncture the piston is 

 gently pressed, causing a bleb to rise in the skin. The syringe is 

 then slowly withdrawn, and again introduced within the periphery 

 of the little blister previously produced. This is quite painless, as 

 the area has now become insensitive. A further blister is thus 

 produced, and the operator proceeds in the same way until a chain 

 of blisters is formed covering the entire length of the incision presently 

 to be made. Each of these points of artificial oedema is insensitive. 

 The method succeeds, not only in the case of skin and mucous 

 membranes, but in serous and synovial membranes, muscles, nerves, 

 and the periosteum. Even bones and the bone medulla can be 

 rendered insensitive by subperiosteal injections. Deeper-lying tissues 

 can, of course, only be rendered insensitive after the more superficial 

 have been so treated. The condition persists for fifteen to twenty 

 minutes ; should an operation last longer the process must be 

 repeated. In preparing for the insertion of sutures for instance, 



