120 BACTERIOLOGICAL DIAGNOSIS. 
Where possible it is preferable to apply a dressing of 
lint soaked in one of the above lotions (which need be 
of only half the strength) for a few hours. 
The puncture may be made by means of some sort of 
exploring syringe, or by means of a hollow needle with- 
out any means for aspiration. The former is used for 
the removal of fluid from the pleura or synovial cavity, 
the latter in performing lumbar puncture. But it is 
necessary that the whole of the instrument used should 
be rendered sterile by heat; chemical antiseptics are 
quite inadmissible. In the case of a hollow needle no 
difficulty occurs ; some hypodermic syringes, however, 
will not stand boiling, and these are useless for the 
purpose, as the apparatus which is to be used must be 
boiled for at least five minutes. 
We shall now deal with the most important cavities 
of the body, describing the methods to be employed in 
the investigation of the inflammatory exudates which 
they may contain, and the inferences which may be 
drawn from the results of the examination. 
THE PLEURA. 
There is but little to be said about the method to be 
employed in the collection of fluid from the pleural 
cavities. The most careful antiseptic precautions are 
to be taken, and the region to be punctured should be 
decided by consideration of the physical signs. 
The examination of the fluid thus obtained may be 
either microscopical, cultural, or by injections into 
animals. If the latter are required (and inoculation 
should be performed in all cases where a tubercular 
