ABERRANT FORMS 229 



and arranged in a more or less parallel manner. Tubercle 

 bacilli are quite devoid of motility. 



Aberrant Forms. Though such are the characters of 

 the organism as usually met with, other appearances are 

 sometimes found. In old cultures, for example, very much 





FIG. 63. Tubercle bacilli in phthisical sputum ; they are longer than 

 is often the case. 



Film preparation, stained with carbol-fuchsin and methylene - blue, 

 x 1000. 



larger elements may occur. These may be in the form of 

 long filaments, which may be swollen or clubbed at their 

 extremities, may be irregularly beaded, and may even show 

 the appearance of branching. Such forms have been 

 studied by Metchnikoff, MafTucci, Klein, and others. Their 

 significance has been variously interpreted, for while some 

 look upon them as degenerated or involution forms, others 



