Let us take first the case of the healthy adult about to undergo a _major_ operation. For this, we unhesitatingly choose what we may term the “stock” method--open-ether preceded by morphia and atropine. If the operation be _brief_, we have a choice of methods. For the extraction of teeth, where access to the mouth is essential, the following table will help:-- +------------------------+---------------------------+-------------------------+ | |Duration of Available | | |ANÆSTHETIC DRUG AND | Anæsthesia, when | REMARKS. | |METHOD. | given as “Single | | | | Dose.” | | +------------------------+---------------------------+-------------------------+ |Nitrous oxide |30 to 40 seconds | | |Nitrous oxide and |40 to 50 seconds | | | oxygen | | | |Ethyl chloride |70 to 90 seconds |Only to be recommended | | | | in special cases (_see_| | | | page 127). | |Gas and ethyl chloride |70 to 90 seconds | | |Gas-oxygen and ethyl |70 to 90 seconds | | | chloride | | | |Gas and ether |Anything up to 2 to 5 |May cause after vomiting.| | | minutes according to | | | | duration of inhalation | | |Ethyl chloride and ether|Anything up to 2 to 5 |May cause after vomiting.| | | minutes according to | More portable. | | | duration of inhalation | | |Nasal gas |5 to 10 minutes (not a |Requires considerable | | | “single dose” anæsthetic)| practice to give well. | |Nasal gas and oxygen |No limit |Easier to give than | | | | above but apparatus | | | | rather importable. | +------------------------+---------------------------+-------------------------+ In cases where access to the mouth is not required, and where it is therefore unnecessary to “charge up” the patient with anæsthetic, we have also a choice which may be expressed tabularly:--