68 OPERATIVE TECHNIQUE. 



He showed that it is not necessary to inject strong solutions of 

 the anaesthetics which might produce poisoning, but that quite weak 

 solutions, even a "i per cent, solution of chloride of sodium, suffice, 

 and that in all cases of anaesthesia, other factors than the mere 

 chemical constitution of the substance play an important part. The 

 injection of fluids under fairl}^ high pressure into the skin and sub- 

 cutaneous tissues renders the whole area affected completely insensitive. 

 Should the tissues be cut through no blood flows. 



This method produces anaesthesia by the co-operation of four 

 factors — the pressure induced by the mechanical action of the liquid, 

 cold due to the temperature of the solution, anaemia caused by the 

 cold and pressure, and a chemical change produced in the nerve 

 endings. The undermentioned formulae, which ha\e been used in 

 human practice since 1894, have been lately used upon horses and 

 dogs by Podkopajeu and Negri, who recommend them for their 

 simplicit}', 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 recom- 

 mends the following formulae for use in man : 



r Hydrochloride of cocaine 



h 



„^ 1 i- r Hydrochloride of morphine 



btronar solution -J ^/, -j r j- 



° I Chloride of sodium 



I Water 



0-20 

 002 



0-20 



100 



7 fluid drachms injected at each operation. 



r Hydrochloride of cocaine . . . o'lo 



,. , ^ , ^ 1 i- I Hydrochloride of morphine . . 002 



Moderately strongf solution^ ^/, -j r -i- ^.^„ 



-' '^ I Chloride 01 soduim . . . o 20 



V Distilled water .... lOO 

 14 fluid drachms injected at each operation. 



/"Hydrochloride of cocaine .... O'OI 



.,. 1 , ,- I Hydrochloride of morphine .... o'OOs 

 V\ eak solution -, r-i"i -j r j- ^.^^ 



I Chloride or sodium .... o 20 



V Distilled water ..... lOO 

 Use up to 140 fluid drachms at each operation. 



He renders even the first prick of the needle painless b}- 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 lo 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 S}Tinge is then 

 slowl}- withdrawn, and again introduced within the peripher}^ of the 



