

MORPHOLOGY 



313 



by clear unstained intervals. They are sometimes straight but more often 

 somewhat S-shaped or bent on themselves. 



[According to Eastwood (working for the English Commission) mammalian 

 tubercle bacilli when grown on serum are of a very uniform character ; 

 straight, uniformly stained and about I/A long but ranging from 0'75-2'5/x. 

 On media containing glycerin the average length is greater : in the same 

 film, short (1/x) bacilli, longer (2-4/A) forms and very long (5-7 or S/A) forms 



FIG. 202. 



FIG. 203. 



FIG. 202. Tubercle bacilli from a culture. 2 months old, on glycerin-agar, 

 of a typical avian virus. In addition to short forms, long branching forms are 

 found. The branching frequently emanates from a darkly stained spherical 

 point, which in some instances is of a greater diameter than the breadth of the 

 bacillus. Branching is much commoner with the avian than with the mam- 



malian bacillus. Carbol-fuchsin. 



2150. 



(Eastwood.) (See footnote p. 295.) 

 FIG. 203. Tubercle bacilli from a culture, 2 months old, on glycerinated 

 potato, of a typical avian virus (same virus as fig. 202). The bacilli show a 

 tendency to grow in long, parallel threads. Carbol-fuchsin. x 2150. (East- 

 wood.) (See footnote p. 295.) 



may all be encountered and on these media the bacilli are frequently curved 

 and many are stained irregularly (beaded and globular forms). Branched 

 forms are very rarely indeed seen in cultures. 



[Avian tubercle bacilli grown on glycerin serum are generally very short 

 (0'5-1/A) and rather thick. On other media they are as a rule longer and 

 more irregular. Among these irregular forms can be found examples of all 

 the forms assumed by the mammalian bacilli ; and large club-shaped swellings 

 are not uncommonly seen while 

 branching occurs more frequently 

 than with the mammalian bacillus. ] 



Koch regarded as spores the un- 

 stained intervals which are some- 

 times seen in the bacilli. There is 

 now a tendency to regard the deeply 

 stained granules seen at the ends or 

 in the length of some bacilli as 

 spores (Babes, Ehrlich). Gavina 

 thinks that he has stained terminal 

 spores in bacilli grown in presence of 

 antiseptics. 



In cultures extraordinarily short 

 bacilli are occasionally seen. 

 other cases, particularly in old cul- 

 tures, large, branched bacilli endine 

 in a club-shaped swelling are foun 

 (%. 204). 



These giant forms afford 



FIG. 204. Involution forms of the tubercle 

 bacillus. (After Metchnikoff.) 



