24 



CANINE AND FELINE SURGERY. 



the removal of small superficial tumours, and are not readily 

 applied to thick muscular tissues where a considerable amount of 



Fig. 12. 

 Glass tube containing ethyl chloride ready for application. 



dissection has to be done ; the reasons being that if a thin layer 

 only be frozen the warm blood (when the incision is made) pre- 

 vents the further application of the anaesthetic, whilst if the whole 

 mass be frozen first it is difficult to cut, and there is the danger 

 of necrosis as a sequel. 



As a general rule anaesthesia is produced when the skin has 

 turned white ; this occurs in from half a minute to a minute and 

 a half, and the effect lasts for about two minutes.^ Care must 

 be taken not to keep the parts frozen for too long a time, or 

 necrosis may follow. 



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 orthoform, 

 which owe their special function to their power of paralysing 

 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 possess- 

 ing exactly the same formula. 



1 ".Journal of Comparative Pathology and Therapeutics," Vol. IX., p. 227. 



