GALVANIC AND THERMOCAUTERIES. 95 



of the iron causes violent struggling. Cauterisation can be dispensed 

 with by applying before section an elastic bandage to the tail just 

 above the point of division. It has been suggested that the bandage 

 should be left in position for a week, but this would be dangerous, 

 and it is sufficient to leave it twelve to twenty-four hours. 



The Galvanic and Thermo-cauteries. In the galvanic cautery 

 a loop of platinum wire is passed around the tissue to be divided, 

 and after being raised to a bright red heat by the passage of an 

 electric current, is gradually drawn tight. On account of its com- 

 plexity and expense, however, this instrument is very seldom used 

 in veterinary surgery, especially as Paquelin's thermo-cautery (Figs. 

 113, 114) renders almost equally good service and is much cheaper. 

 The thermo-cautery consists of a hollow platinum terminal which 

 may be of varying shape. After being heated in a spirit flame it is 

 kept at a bright red heat by injecting a mixture of ether or benzine 

 vapour and air into the head. Tissues divided by this instrument 

 bleed very little, though the scab produced by the cautery must 

 have a certain thickness, to attain which the division must be made 

 deliberately. The wounds produced heal comparatively slowly. 

 (For other cauteries, see pp. 155-160). 



Puncture. A puncture is an incision of considerable depth but 

 of comparatively small diameter. Puncture to permit fluids or 

 gases to escape from cavities, like the thorax, abdomen, or bowel, 

 is termed paracentesis. To prevent the entrance of air into deeper 

 seated tissues or into the cavity to be opened, the skin is often drawn 

 to one side before operation, so that returning afterwards to its 

 ordinary position it closes the deeper opening. Subcutaneous puncture 

 may also be practised by first introducing the perforating instrument 

 horizontally a short distance under the skin, and, after altering its 

 direction, making the desired puncture ; the walls of the opening 

 immediately collapse on the removal of the instrument. 



An ordinary pointed knife, bistoury, scalpel or lancet may be 

 used for puncturing. The knife is held like a pen, the thumb on 

 one, the index and middle finger on the other side, the little finger 

 being used as a support. The point is caused to enter vertically 

 by extending the previously bent fingers. In withdrawing the instru- 

 ment the opening may, if necessary, be enlarged (Figs. 120, 121). 

 In using a bistoury or lancet the handle is held at right angles 

 to the blade. Many persons grasp the blade, only leaving uncovered 

 sufficient to penetrate to the desired depth ; but this method, 

 however, has the disadvantage that in case of a mistake in regard to 

 the thickness of the tissues to be divided the fingers must be moved, 



