THE TUBERCLE BACILLUS 263 



chains~are not formed, but occasionally short filaments are met 

 with. In cultures the bacilli form masses in which the rods are 

 closely applied to one another 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 larger elements 





FIG. 78. Tubercle bacilli iu phthisical sputum ; they are longer than 



is often the case. See also Plate II., Fig. 7. 



Film preparation, stained with carbol-fuchsin and inethylene-blue. 

 xlOOO. 



may occur. These may be in the form of long filaments, some- 

 times 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, Maffucci, Klein, and 

 others. Their significance has been variously interpreted, for 

 while some look upon them as degenerated or involution forms, 

 others regard them as indicating a special phase in the life 

 history of the organism, allying it with the higher bacteria. 

 Recent observations, however, go to establish the latter view, 

 and this is now generally accepted by authorities. It has also 



