54 BACTERIOLOGY. 



developing as fours (Fig. 2, d); and saroince those 

 dividing into fours, eights, etc., as cubes that is, in 

 contradistinction to all other forms, the segmentation, 

 which is rarely complete, takes place regularly in three 

 directions of space, so that when growing the bundle of 

 segmenting cells presents somewhat the appearance of a 

 bale of cotton (Fig. 2, e). 



To the bacilli belong all straight, rod-shaped bacteria 

 i. e., those in which one diameter is always greater 

 than the other. 



In this group are found those organisms the life- 

 cycle of many of which presents deviations from the 

 simple rod-shape. Many of them in the course of 

 development increase in length into long threads, 

 along which traces of segmentation may usually be 

 found the anthrax bacillus and bacillus cereus are 

 conspicuous examples of this. Again, under certain 

 conditions, many of them possess the property of form- 

 ing within the body of the rods oval, glistening spores 

 (see Fig. 6), and, if the conditions are not altered, the 

 rods may entirely disappear and nothing be left in 

 the culture but these oval spores. In some of them 

 this phenomenon of spore-formation is accompanied by 

 an enlargement or swelling of the bacillus at the point 

 at which the spore is located (see Fig. 6, e and d). 

 Again, many of them, from unfavorable conditions of 

 nutrition, aeration, or temperature, undergo pathological 

 changes that is, the individuals themselves experience 

 degeneration of their protoplasm with coincident dis- 

 tortion of their outline ; they are then usually referred 

 to as "involution-forms" (see Fig. 5, a and 6). In 

 all of these conditions, however, so long as death has 

 not occurred, it is possible to cause these forms to revert 



