256 TUBERCULOSIS. 



the surrounding fatty medium. We have found that in smegma it can 

 be readily decolorised by a minute's exposure to alcohol after the usual 



treatment with sulphuric 



j . acid, and thus can be 



s readily distinguished 



-A \"*' from the tubercle bacillus. 



* We, moreover, believe 



, *\ \* that minor points of dif- 



i ' r i 



I ference in the microscopic 



* _ . appearances of the two 



I %. * organism s are quite 



sufficient to make the 



p , , t experienced observer 



'ijJ X t x * suspicious if he should 



. fl+ ^ M . . t . t 



i V, 



' meet with the smema 



" bacillus in urine, and 



^/ -^ ^ijj lead him to apply the 



I 4 ^ \ decolorising test. Diffi- 



1**^ culty will only occur 



when a few scattered 

 bacilli retaining the 



FIG. 68. Smegma bacilli. Film prepara- fuchsin occur, 

 tion of smegma. 1 ts cultivation is 



Ziehl-Neelsen stain. x 1000. - attended with much diffi- 



culty. In fact, Czap- 



lewski alone appears to have succeeded. On serum it grows in the 

 form of yellowish-grey irregularly rounded colonies about i mm. in 

 diameter, sometimes becoming confluent to form a comparatively thick 

 layer. He found that it also grew on glycerine agar and in bouillon. 

 It is non-pathogenic to various animals which have been tested. 



Methods of Examination. (i) Microscopic examination. 

 Tuberculosis is one of the comparatively few diseases in 

 which a diagnosis can usually be definitely made by micro- 

 scopic examination alone. In the case of sputum, one of 

 the yellowish fragments which are often present ought to be 

 selected ; dried films are then prepared in the usual way 

 and stained by the Ziehl-Neelsen method (p. 113). In the 

 case of urine or other fluids a deposit should first be 

 obtained by centrifugalising a quantity in a test-tube, or by 

 allowing the fluids to stand in a tall glass vessel (an ordinary 

 burette is very convenient). Film preparations are then 

 made with the deposit and treated as before. If a negative 

 result is obtained in a suspected case, repeated examination 



