TEXT-BOOK OF BACTERIOLOGY. 11 



yet only been tlioroughly investigated and followed through its 

 details in three different rod species: in the Bacillus subtil is of F. 

 CoLn, in the Bacillus anthracis of Koch, and in the Bacillus megate- 

 rium of De Bary. 



What has been elicited in brief is as follows : 



At the commencement of the spore-formation, the protoplasmic 

 contents of the bacterial cell concentrate at certain pohits, which 

 appear to the eye as darker portions of different refractive power. 

 These coalesce, while the rest of the cell contents becomes clear and 

 light-colored. The fully-formed spore then appears as a strongly- 

 refracting, bright-gleaming body of definite (generally egg-shaped) 

 form, with a regular dark outline, a thick spore membrane sur- 

 rounded by the rest of the spore-bearing cell, which is as clear as 

 water. 



This latter soon perishes entirely, the membrane dissolves and 

 disappears, the spore is free, and the process is at an end. 



This is s^en in threads of the Bacillus anthracis after completion 

 of the spore-formation. Cell after cell is seen, each bearing in the 

 middle the bright-gleaming spore, so that the whole resembles a 

 well-arranged string of beads. In addition to these a few free 

 spores may be seen, which, as a rule, show a brisk molecular motion. 



One cell forms only one spore, under all circumstances. It may 

 have its seat in the middle, as just described, or in other cases at 

 the end of the rod. The latter often undergoes no change of shape 

 in the sporulation; but it may swell and widen at the place where 

 the spore afterward forms, and the sporulation takes place in the 

 cell thus modified. In the cases of spores which grow in the middle 

 of the bacteria cells, peculiar spindle or shuttle-shaped forms, with 

 a stout body and short pointed ends, the so-called clostridise de- 

 velop, while sporulation from the end of a cell leads, under similar 

 circumstances, to the development of the " drummer bacteria " and 

 "headed bacteria," in which the spore is located at one end of the 

 poles of the cylinder, which presents a club-like swelling. 



Of what the contents of the spore really consist is still unknown. 



That a very early and thorough separation within the bacterial 

 cell, between that part of the protoplasm which goes to form the 

 spore and the remainder of its substance, occurs, may be perceived 

 from the coloring. Several investigators have called attention to 

 the fact that in the interior of many micro-organisms about to 

 form spores, certain grains and globules are found which, under the 

 influence of suitable staining processes, are easily distinguished 

 from the rest of the body. 



The view has even been maintained that these sporogenic grains 



