LOCAL ANESTHESIA. g9 



less modified, the mode of its employment continues unchanged ; 

 though any substance susceptible of easy pulverization may be 

 employed. Ether is the agent most frequently chosen. Rigolene 

 has given us great satisfaction in our own practice. 



In impinging upon the skin in a state of excessive division, 

 the rapid evaporation of the liquid lowers the temperature of the 

 surface with which it comes in contact, and it is this process of 

 refrigeration which diminishes the local sensibility, and, as the 

 effect increases, overcomes it entirely for the time beiag, or so 

 long as the spray continues to be thrown upon the part. 



Some sUght objections, however, may be alleged agaiast this 

 mode of producing insensibility, arising from the special proper- 

 ties of the fluid employed, and for this reason the mode by sub- 

 cutaneous injection is somewhat to be preferred. 



2d. Subcutaneous Injections. — Both ether and chloroform 

 have been recommended, and extensively used, m. this manner, 

 but without doubt the salts or compounds of cocaiae possess ad- 



FlG. 65.— Syringe of Pravaz. 



vantages over either of them. An epidermic syriage, or that of 

 Pravaz, is generally used for the purpose, with a solution of from 

 four to twenty per cent, strength, according to circumstances. 



If used on a tumor a certain quantity of the solution, perhaps 

 twenty drops, is injected imder the skin at two or three points 

 around its circumference, the desired effect following, and the 

 parts being ready for the operation within from eight to ten 

 minutes, more or less, according to the strength of the dose 

 administered. Either of these modes of local anesthesia is harm- 

 less, and may be employed without risk or fear of complications. 



