ANAESTHETICS 75 



are allied to anodynes, but act more promptly and power- 

 fully. Certain volatile drugs, brought into contact with the 

 nerve-cells, reduce or arrest for considerable periods their 

 functional activity, probably in virtue of chemical action. 



Local anaesthetics produce paralysis of the peripheral 

 endings of sensory nerves. They include cocaine, stovaine, 

 eucaine, holocaine, ethyl-chloride, methyl-chloride, carbolic 

 acid, antipyrine, iodoform, orthoform, and extreme cold. 

 Cocaine is generally preferred. The part is painted or in- 

 jected with a solution of the hydrochloride, until the 

 requisite insensibility is secured. Cocaine proves particu- 

 larly serviceable in diminishing irritability, and facilitating 

 examinations of the eye and larynx, as well as for the 

 performance of minor operations. 



General anaesthetics, when inhaled, are carried by the 

 blood-stream to the centres of the brain and cord, which 

 they paralyse, producing unconsciousness. They comprise 

 nitrous oxide gas, chloroform, ether, and other substitution 

 compounds of the methane (CH 4 ) and ethane (C 2 H 6 ) series. 

 Nitrous oxide produces its effects rapidly, induces a general 

 anaesthesia, which can, however, only be kept up for a very 

 short time one to two minutes because of the asphyxia 

 which is produced. This is shown by the venous condition 

 of the blood, cyanosis of mucous membranes, with con- 

 traction of arterioles and rise of blood-pressure, and there 

 is hence no risk of its causing syncope. Admixture with 

 oxygen prevents asphyxia, but lessens and delays the 

 anaesthesia. In human practice, anaesthesia is often induced 

 by nitrous oxide, and subsequently maintained by chloro- 

 form or ether. Chloroform is generally used both in human 

 and veterinary practice. It is the most effectual and, 

 rightly used, the safest known anaesthetic. It acts in 

 smaller quantity, more rapidly, and with less excitement 

 than ether. Ether, first employed in America, is preferred 

 by many English practitioners, on the plea that it is less apt 

 than chloroform to impair cardiac action. But it has the 

 disadvantage of greatly increasing bronchial secretion and 

 salivation, of causing more irritation and excitement than 

 chloroform, while its administration requires the use of an 

 inhaler. 



