262 BACILLI PATHOGENIC IN MAN. 



the most part the bacilli are slightly bent, or even more 

 frequently curved. They are often spore-bearing, the 

 number of the spores being usually 2 4 or even 6. By 

 the ordinary method of treating the preparations the 

 spores do not take up the colouring matter, and hence 

 the spore-bearing bacillus when stained presents the 

 appearance of a dark thread, interrupted by clear egg- 

 shaped spaces. At times it seems as if the spores pro- 

 jected laterally beyond the con- 

 tour of the bacillus. If the 

 specimen is examined with in- 

 sufficient magnification one 

 readily obtains the impression 

 that such a spore-bearing thread 

 is composed of a chain of cocci ; 

 if the preparation is badly 

 stained, too much heated, or too 



Fig. 72. Sputum containing long treated with acid, this ap- 

 pearanceisincreased. Neverthe- 

 less it is always possible, in carefully prepared specimens 

 and with the aid of good lenses (Zeiss r V, Winkel ^V), 

 to convince oneself that the supposed chain of cocci does 

 not exist, but that the delicate contour of the bacillus 

 can be for the most part traced through its whole length, 

 and that it is only within this contour that the alter- 

 nation of stained and unstained zones gives the deceptive 

 appearance of stained cocci separated by narrow inter- 

 mediate spaces. The assertion made by some observers 

 that the tubercle bacilli also occur in the form of cocci 

 can only be referred to this and other errors of obser- 

 vation. In all cases the tubercle bacilli appear 

 to be non-motile. ft ^ 



situation of The bacilli are most readily found where the J (J 

 tubercular process is commencing or spreading. 

 At first the bacilli are single, and then almost Fig 73. 

 always lie in the immediate neighbourhood of a bacilli x 

 nucleus and in the interior of the cell to which 120 - 

 this nucleus belongs ; later they occur in closely packed 

 small masses. The cheesy centre of the mass shows 

 only broken down nuclear substance, which no longer 



