76 BACTERIOLOGICAL DIAGNOSIS. 
tubercle bacilli in large numbers. The advantage of 
getting the patient to wash out his mouth and using 
only fasting sputum is obvious, for particles of food 
may present exactly the same appearance. 
Having found such a mass pick it out by means of a 
platinum loop or pair of forceps and transfer it to the 
middle of a clean slide. Now place another slide on 
the top of the first, squeeze them together and then 
slide them apart. You should get two good uniform 
films. Dry and fix. 
If there are no caseous masses pick out a mass of the 
sputum at random and proceed as before. 
A better method is as follows:—Half fill an ordinary 
medicine bottle with carbolic lotion (1 in 20) and adda 
drachm or two of the sputum. Shake thoroughly for a 
few minutes and place the bottle where you can give it 
an occasional shake during the next few hours. Then 
pour the milky emulsion which results into a conical 
urine glass and allow it to stand for twelve hours or 
more. Remove some of the deposit which will form 
with a pipette and spread it into a thin film on a slide. 
Dry and fix. 
Urine is treated in a similar way; but here carbolic 
acid (liquefied or in crystals) is added to the urine in 
amount sufficient to convert it into a 1 in 20 solution. 
This is allowed to deposit or (better) is centrifugalised. 
Films are prepared from the deposit. 
Remember that they should be passed through alcohol 
after staining. 
Pus is best carbolised in the same way as sputum; if 
very thin it may be treated like urine. The tubercle 
bacilli will rarely be found in pus unless it is examined 
soon after the abscess is opened, but may be detected 
by inoculation experiments for long periods. 
