PATHOLOGICAL EXUDATES. IIg 
and cord, and the joints. In some cases all the needful 
information may be obtained by the examination of 
stained films, cultures being unnecessary ; and in these 
cases no anti- or aseptic precautions (other than those 
which are dictated by the interests of the patient) are 
necessary. But in the greater proportion of cases this 
is not enough, and cultures must be obtained. To this 
end it is absolutely essential that the most scrupulous pre- 
cautions should be taken against contamination of the 
fluid by the organisms which are constantly present in 
the air and in the skin, or the results will be worthless. 
The precautions taken must be as complete as those 
which are used before an operation upon a joint. 
Indeed, a fresh precaution has to be taken, for whereas 
the presence in the skin of a small quantity of an anti- 
septic would not be detrimental to a surgical operation, 
it might, by getting into the fluid, nullify a bacterio- 
logical examination. Hence the skin must be aseptic 
and free from any antiseptic chemical. 
The technique, as far as aseptic precautions are con- 
cerned, is as follows:—The skin at the region to be 
punctured is first thoroughly cleaned with soap, hot 
water, and (if the patient can stand it) a nailbrush. 
Then layer after layer of some reliable antiseptic lotion 
is painted on, each layer being allowed to soak in before 
the next is applied. The most suitable lotions for the 
purpose are perchloride of mercury (1 in 1000) biniodide 
of mercury, (1 in 500 of methylated spirit) or carbolic 
acid (1 in 20). 
After being allowed to act for at least ten minutes 
the skin is to be thoroughly cleansed with methylated 
spirit ; this should be rubbed in with a piece of cotton- 
wool and should be poured copiously over the area. 
The operation may now proceed. 
