26 CANINE AND FELINE SURGERY 



The above-mentioned agents have the advantage over 

 other drugs of not being in any way absorbed so as to 

 produce toxic effects, unless inhaled through the respiratory 

 passages, and even in that case plenty of warning would be 

 given by the patient. 



For operations on the cornea of the eye they are not 

 suitable, on account of the amount of irritation set up. 



We now come to cocaine, eucaine, holocaine, and ortho- 

 form, which owe their special function to their power of 

 paralyzing nerve terminals in the tissues to which they are 

 applied. 



Cocaine is a vegetable alkaloid obtained from the leaves 

 of the coca plant, whilst eucaine is a chemical preparation 

 possessing exactly the same formula. 



The hydrochlorate of each is the salt generally made 

 use of. 



Both of them are toxic, even in very small doses, and great 

 care has to be exercised in their ttse ; they are readily absorbed 

 into the system from subcutaneous, serous, or mucous surfaces, 

 particularly from the first named. 



Cocaine hydrochlorate is readily soluble in cold or warm 

 water, but decomposes on boiling ; the solutions made use 

 of vary from i to lo per cent. It should always be made 

 fresh when required, as even after a few days the efficacy 

 of the solution is not to be relied upon. If it is absolutely 

 necessary to keep it in solution, a small quantity of either 

 salicylic or boracic acid added to it will help to preserve it 

 for a longer time. 



After an injection complete local anaesthesia is produced 

 in from three to five minutes, and lasts about twenty or 

 twenty-five minutes ; its effect is manifested around the seat 

 of injection for a space of from half an inch to li inches, so 

 that where a large incision or large tumour is concerned 

 injections must be made in several places. Superficially it 

 can be used to deaden pain when painted on parts (such as 



