MORPHOLOGY AND PHYSIOLOGY OF BACTERIA. 1 19 



The bacilli are not usually subdivided in this manner, 

 although their forms vary considerably. The ends are 

 sometimes square, sometimes round. Sometimes they are 

 very short. Sometimes they grow in longer, thread-like 

 forms, in which, however, the transverse markings which 



FIG. 40. 



-& 



Bacilli of Various Forms. 



indicate the outlines of the individual bacilli can generally 

 be seen, and which resemble a bamboo rod. Short oval 

 bacilli may look exceedingly like micrococci. Bacilli with 

 rounded extremities, placed end to end, look like strings of 

 sausages. Under exceptional circumstances, branching 

 forms of the bacilli of diphtheria, tuberculosis, glanders and 

 bubonic plague and various other species have been en- 

 countered. 1 



The word ce bacterium " was formerly used to designate 

 short bacilli which generally formed no spores, while the 



FIG. 41. 



Spirilla of Various Forms. 



word bacilli was restricted to the longer forms in which 

 spore formation occurred. This use is no longer common, 

 although not rarely the name bacterium is still given to a 

 species for instance, bacterium coli commune. 



1 See Hill, Journal of Medical Research, Vol. VII., January, 1902; 

 Loeb, ibid., Vol. VIII., 1902. 



