THE BACTERIA IN GENERAL 25 



The spores formed by the bacteria are of two kinds, arthrospores 

 and endospores. Arthrospores are whole vegetative cells which by a 

 thickening of their walls become resting spores. Some bacteriologists 

 would not include arthrospores as true spores. The true spores are 

 formed in the cells and differ from the cells in resisting greater heat 

 and by other definite structural and physiologic quaUties. (Fig. 7.) 

 The shape of the cell may be altered with the formation of one or two 

 spores within (endospores). In the hav bacillus, the spore occupies the 

 center of the cell and is smaller than the original mother cell, hence the 

 shape of the parent cell is not altered. Bacterium pants and Bacillus 

 amylobacter become swollen in the middle when the spore forms so that 

 the mother cell becomes spindle-shaped. The bacillus of lockjaw de- 

 velops a spore at one end of the cell, which becomes drumstick-shaped, 

 hence the German name trommelschlagel for such forms and the generic 

 name Plectridium now given to cells that produce terminal spores. 



Bacillus amylobacter may develop one terminal spore, or two spores, 

 one at each end of the cell, so that the mother cell becomes dumbbell- 

 shaped. Bacillus inflatus may develop two spores also. 



Spores may germinate at the poles, as in Bacillus BiitscJili and B. 

 amylobacter ; at the equator, as in Bacillus subtilis and B. loxosporus, or 

 obliquely, as in Bacillus loxosus. In germination resting spores absorb 

 water, and become more or less swollen, when the spore membrane 

 is dissolved and the germ tube protrudes. 



The classification of bacteria according to their special activities, 

 or the products formed by these activities, is useful in presenting 

 another phase of the subject to the mycologic student. The fact is 

 noteworthy that we can group the various organisms into the photo- 

 genic (light-producing), chromogenic (color-producing), thiogenic 

 (sulphur-producing), zymogenic (ferment-producing), pathogenic (dis- 

 ease-producing), saprogenic (decay-producing) and thermogenic (heat- 

 producing) without reference to their morphology, or genetic rela- 

 tionship. It is useful to be able to discuss the light, heat, color, etc., 

 produced by these organisms as distinct phenomena worthy of experi- 

 mental treatment. 



Photogenic Bacteria. — The phosphorescence associated with decaying 

 haddocks, mackerel and other sea fishes, the faint glow seen on badly 

 preserved meats (beef, mutton, veal) and sausages are produced by 

 photogenic bacteria. Most success is obtained by using sea fishes in 



