40 



BACTERIOLOGY. 



segments of a spiral. Here, too, we have large and 

 small, slender and thick spirals. The twisting of the 

 long axis, which here lies in two planes, is the chief 

 characteristic of this group of bacteria. Under normal 



FIG. 8. 



FIG. 9. 



Medium-sized spirilla. 



conditions the twisting is equal throughout the entire 

 length of the cell. The spirilla, like the bacilli, divide 

 only in one direction. A single cell, a pair, or the 

 union of two or more elements may thus present the 

 appearance of a short segment of a spiral or a comma- 

 shaped form, an S-shaped form, or a complete spiral 

 or corkscrew-like form. 



Among uncommon morphological peculiarities in 

 true bacteria may be mentioned dichotomy, or branch 

 formation that is, a side growth projecting from the 

 bacterial cell. True dichotomous branching has occa- 

 sionally been observed in the bacilli viz., the bacilli 

 of tuberculosis, diphtheria, and glanders. 



Summary of Morphological Forms of Bacteria. 1. 

 Coccus, or micrococctis. Spherical or subspherical 

 forms. 



