PUNCTURE OF THE THORAX. 
247 
so-called aspirator (fig. 119) consists of a rubber tube, hollow needle, and 
large syringe provided with a tap. The hollow needle is inserted, the 
piston raised, and when the syringe has become full, the tap is turned, 
and the contents discharged. The process is then repeated. The aspirator, 
however, has been little used in veterinary surgery. The same object 
is more easily attained by pushing one end of a suitable indiarubber 
tube over the free opening of the canula, and dropping the other end 
into water. This syphon-like arrangement exerts an aspirating action on 
the contents of the thorax, but has the disadvantage that the outflow 
cannot be exactly controlled, while forcible aspiration may rupture 
pleural vessels. 
While using the ordinary instrument, if it be required to check the 
outflow of fluid, or prevent entrance of air, and especially if excita¬ 
bility, dyspnoea, and coughing set in, the trochar must be removed. 
The necessity of removing pleuritic effusion gradually, points to the 
Fig. 120.—Special trochar and canula. The second limb is provided with a long 
rubber tube, allowing the instrument to lie used as an aspirator. 
use of trochars of moderate calibre. In carnivora, and to a less 
extent in horses and oxen, rapid discharge of large quantities of 
fluid is liable to produce sudden changes of intra-thoracic pressure, 
determining grave disturbances of circulation, which may occasion not 
only fresh extravasation, but pulmonary bleeding, syncope, or even 
sudden death. The danger is greatest in left-side extravasations, by 
which the heart has been pushed towards the right side. It is, therefore, 
advisable in horses and cattle to remove only 10 to 15 pints at one time, 
and a further quantity some hours later, or on the following day. 
From the position of the tapping, the complete evacuation of the pleural 
sac is impossible; but even if it were possible, as already pointed out, 
it would not be desirable. In too many cases fresh extravasation soon 
takes place. When sufficient fluid is believed to have been removed, the 
stilette, previously cleansed, is again introduced, and the canula carefully 
removed, the wound rinsed with a disinfectant, powdered with iodoform, 
and closed with wound gelatine or collodion. A simple application of 
tar may be sufficient, but a suture is sometimes inserted. The benefits 
of paracentesis mainly result from its modifying intra-thoracic pressure, 
