PUNCTURE OF THE THORAX. 
245 
disinfectants. No permanent benefit results from removing blood from 
the pleural sac, because if the membrane is not seriously diseased 
absorption rapidly occurs. In perforating wounds of the chest, the 
early injection of antiseptics, and performance of paracentesis, may 
prevent injurious effects from decomposition of extravasated fluid ; but in 
chronic hydrothorax, which has resulted from impaired circulation or 
change in the composition of the blood, it only hastens death. 
(1.) Puncture of the Thorax for Removal of Serous or Pleuritic 
Exudate.— The trocliar used for the larger animals has a diameter 
of \ inch ; but one of smaller calibre is usually preferable. Side openings 
in the canula are not of particular value. Various precautions require 
to be observed 
(1) Carefully disinfect the instrument and site of operation. 
(2) Prevent entrance of air into the thorax. 
(8) Remove contents slowly, to minimise interference with circulation. 
The patient, if possible, should stand, as the recumbent position 
only adds to the difficulty of the operation. This applies equally to 
the smaller animals especially if there is much dyspnoea. Dogs with 
hydrothorax sometimes die in a few minutes from being placed on the 
side. The operation is not now performed as low down as formerly. 
In all animals the opening should be made either slightly above or 
slightly below the subcutaneous thoracic vein, keeping clear of the large 
pectoral muscle, which lies still lower. The upper position deserves 
preference. Where both pleural sacs contain fluid, the operation should 
be performed on the right side, to prevent injuring the heart. The 
vertical boundary for punctures lies in the horse between the 5th and 
8th ribs; in oxen, between the 6th and 8th; in swine, between the 7th 
and 9th ; and in carnivora, between the 5th and 9th. In actual practice 
the ribs are often disregarded, and in the horse the puncture is made 
a span behind the point of the elbow. (For relations of the ribs to 
thoracic contents, see figs. 148 and 144.) 
The hair is first shaved from the site of operation, the skin washed 
with soap and rinsed with aether, and finally saturated with such 
disinfecting fluid as diluted sublimate. Similar care must be taken 
in disinfecting the trochar. In private practice this is most easily and 
safely effected by boiling the instrument in water, or laying it in a 8 
to 5 per cent, solution of carbolic acid. To facilitate the entrance of the 
instrument, often difficult in animals with thick skins, an incision is 
first made with a bistoury or lancet. The trochar, grasped with the 
handle in the hollow of the right hand, is supported with the thumb 
and fingers, while the index finger, more or less extended, is fixed 
on the canula at the point to Avhich the trochar is to enter. This 
