50 BACTERIOLOGY. 



marked and characteristic forms result. Thus, in the 

 case of a median spore a marked enlargement of the central 

 portion of the cell gives rise to a spindle-shaped form 

 which is known as a clostridium (Fig. 13 a 2). When the 

 spore is terminal, a corresponding spherical enlargement of 

 the end gives rise to what is known as the "drum-stick" 

 bacillus (Fig. 13 c 2). 



FIG. 13. Position of spores; resultant forms (diagrammatic). 

 a Median spores; Intermediate spores; c Terminal spores; 

 2 a, b, c Change in form of cell due to the presence of the spore; 

 2 a Clostridium; 2 c " Drum-stick " form. 



In the case of motile bacteria spore production is 

 usually accompanied by a loss of motion. This is especially 

 true of the aerobic species. On the other hand the anaero- 

 bic bacteria may continue to move about for some time 

 after the spore has fully developed. Flagella can be 

 demonstrated on these motile spore-bearing rods. The 

 persistence of motion in such cases may be due to the 

 remnant of protoplasm which is left outside of the spore 

 and which lines the cell wall. 



Spore formation has been supposed to take place when- 

 ever the culture medium became exhausted. This view, 

 however, can be easily shown to be incorrect. The nour- 

 ishing material of the soil is by no means consumed when 

 a given organism begins to form spores. There may be 

 times, however, when this factor may come into play. 

 Under the artificial conditions of the laboratory it is more 

 likely that the accumulation of the waste-products of the 

 organism and the action of these products on the living 

 cell cause it to pass into the spore form. As long as the 



