PREPARATION OF PURE CULTURES 



209 



with a lens, carefully cut away with a sterilised knife, and 

 transferred to the surface of serum which has been made 

 to solidify in a slanting position. 



The following is Kitasato's method of 

 preparing pure cultures from sputum : — 

 The patient is requested to evacuate his 

 morning sputum into sterilised double 

 capsules. A flake derived from the 

 deeper parts of the respiratory appa- 

 ratus is isolated with sterilised instru- 

 ments, and carefully washed in at least 

 ten watch-glasses fuU of distilled water, 

 one after the other, to remove the 

 bacteria taken up in passing through 

 the cavity of the mouth. The flake is 

 now transferred to glycerine agar or 

 serum. After it has been kept for some 

 fourteen days in the incubator the first 

 colonies form, appearing as circular pure 

 white transparent specks, which project 

 above the surface of the medium. Ob- 

 tained by this method the colonies are 

 flat, shining, and smooth, whereas those 

 obtained by the earlier method from 

 tubercular organs are from the first dry, 

 dull, and wrinkled.' The difference, 

 however, disappears as growth advances, 

 and the whole of the medium becomes 

 covered with a coat consisting of trains 

 of bacilli many times coiled. 



Hammerschlag obtains a luxuriant 

 growth by the addition of mannite and 



F 



^(11 



d 



!> fJM 



[g. 82. — cui.'|-ure of 

 Tubercle Bacillus 

 ON Sbii[;.\[. (After 

 Baumgiirteii. ) 



' [The bacilli of tuberculosis in birds form a permanent wrinkled mem- 

 brane on the medium ; but they differ so much in other respects also that, 



