74 CLINICAL BACTERIOLOGY AND ILEMATOLOGY 



the volume) of 5 per cent, caustic soda, mix thoroughly, again cen- 

 trifugalize, and use the deposit for the preparation of films. 



(2) The use of antiformin has recently become very general. It 

 is a mixture of equal parts of liq. soda3 chlorinate: (B.P.) and 

 15 per cent, solution of caustic soda. It has the power of dissolving 

 mucus, pus, and most organic matter, including bact; ria, which are 

 first killed and ultimately dissolved. The acid-fast bacilli, including 

 the tubercle bacillus, are protected by the fat they contain, so that 

 they are killed and dissolved much more slowly than the other 

 bacteria. 



Method. Add antiformin to sputum in the proportion of i part of 

 the former to 5-8 of the latter. Mix well, and incubate for two to 

 three hours. Then centrifugalize, decant off the superficial layer, and 

 replace it with tap water or perfectly fresh distilled water. Mix the 

 sediment very thoroughly with the water, so as to wash it effectively, 

 recentrifugalize, again decant off the superficial layer, and spread 

 films from the deposit. 



This method can also be used for inflammatory exudates or the clots 

 therefrom : in the former case it is best to add antiformin so as 

 to amount to approximately 10 per cent, in the fluid. A firm clot, 

 e.g., that from a pleuritic effusion, may also be treated in fluid of 

 the same strength. Faeces may be examined in the same way as 

 sputum. 



In the use of either of these methods care must be taken to avoid 

 the addition of any extraneous bacilli, such as might happen, e.g., 

 from the repeated use of centrifugalizing tubes which are not thoroughly 

 cleaned. Acid-fast bacilli, which may be easily mistaken for tubercle 

 bacilli, have also been found in distilled water which has been kept 

 for some time. It is best to use new tubes if possible, or old tubes 

 may be boiled in a mixture of 6 parts of sulphuric acid, 6 parts of 

 bichromate of potash, and 100 of water : or they may be filled with 

 fuming nitric acid and allowed to stand for a few hours. New 

 pipettes should always be used. 



Animal Inoculation. This is the most certain method of diagnosis. 

 The most susceptible and convenient animal for inoculation is the 

 guinea-pig. If the material (sputum, pus, etc.) contains no other 

 pathogenic organisms, it may be injected direct : if it contains many 

 pneumococci or streptococci, it is best to treat it with antiformin 

 (taking care not to allow the process to go on ton long), and 

 inject the centrifugalized deposit, as otherwise the animal may 

 die of septicaemia before tubercle has time to develop. Tissues 

 may be minced fine and treated with antiformin. Urine can usually 

 be centrifugalized and the deposit injected direct, but if there is 

 much pus or many pathogenic organisms it should be treated like 

 sputum. The inoculation is best made into the subcutaneous tissue 

 of the groin. 



If the material contains living tubercle bacilli, even in very small 



