1 6 GENERAL MORPHOLOGY AND BIOLOGY. 



tioned there are cocci which divide in three axes perpendic- 

 ular to one another. These are usually referred to as sarcince. 

 If the cells are lying single they are round, but usually they 

 are seen in cubes of eight with the sides which are in 

 contact slightly flattened. Large numbers of such cubes 

 may be lying together. The sarcinae are, as a rule, rather 

 larger than the other members of the group. Most of the 

 cocci are non-motile, but two motile species possessing 

 flagella have been described. 



2. Bacilli. These consist of long or short cylindrical 

 cells, with rounded or sharply rectangular ends, usually not 

 more than i /z broad, but varying very greatly in length. 

 They may be motile or non-motile. Where flagella occur, 

 these may be distributed all round the organism, or only at 

 one or both of the poles (pseudomonas). Several species 

 are provided with sharply-marked capsules (B. pneumonias). 

 In many species endogenous sporulation occurs. The 

 spores may be central or terminal, round, oval, or spindle- 

 shaped. 



Great confusion in nomenclature has arisen in this group in conse- 

 quence of the different artificial meanings assigned to the essentially 

 synonymous terms bacterium and bacillus. Migula, for instance, 

 applies the former term to non-motile species, the latter to the motile. 

 Hueppe, on the other hand, calls those in which endogenous sporula- 

 tion does not occur, bacteria, and those where it does, bacilli. In 

 the ordinary terminology of systematic bacteriology the word bacterium 

 has been almost dropped, and is reserved, as we have done, as a general 

 term for the whole group. It is usual to call all the rod-shaped varieties 

 bacilli. 



3. Spirilla. These consist of cylindrical cells more or less 

 spiral or wavy. Of such there are two main types. In one 

 there is a long non-septate, usually slender, wavy, or spiral 

 thread (e.g., spirillum of relapsing fever, Fig. i, No. 9). In 

 other species the unit is a short curved rod (often referred to 

 as of a "comma" shape). When two or more of the latter 

 occur, as they often do, end to end with their curves alter- 

 nating, then a wavy or spiral thread results. An example 

 of this is the cholera microbe (Fig. i, No. 10). This latter 



