THE LOWER BACTERIA 15 



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 

 (Fig. 1, k, m, n). In the other type 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 alternating, then a wavy or spiral thread results. 

 An example of this is the cholera microbe (Fig. 1, p). This 

 latter type is of much more frequent occurrence. Among 

 the first group motility is often not associated, as far as is 

 known, with the possession of flagella. The cells here apparently 

 move by an undulating or screw-like contraction of the j>roto- 

 plasm. Most of the motile spirilla, however, possess flagella. 

 Of the latter there may be one or two, or a bunch containing as 

 many as twenty, at one or both poles (Fig. 1, q*). Division takes 

 place as among the bacilli, but in some of the non-septate forms 

 a longitudinal fission may occur. In some species endogenous 

 sporulation has been observed. 



Three terms are used in dividing this group, to which different authors 

 have given different meanings. These terms are spirillum, spiroohsete, 

 vibrio. Migula makes "vibrio" synonymous -with "microspira," which 

 he applies to members of the group which possess only one or two polar 

 flagella; "spirillum" he applies to similar species which have bunches 

 of polar flagella, while " spirochsete " is reserved for the long unflagellated 

 spiral cells. Hueppe applies the term "spiroohsete" to forms without 

 endospores, "vibrio" to those wifh endospores in which during sporula- 

 tion the organism changes its form, and " spirillum " to the latter when 

 no change of form takes place in sporulation. Flugge, another systematist, 

 applies "spirochsete" and "spirillum" indiscriminately to any wavy or 

 corkscrew form, and "vibrio" to forms where the undulations are not 

 so well marked. It is thus necessary, in denominating such a bacterium 

 by a specific name, to give the authority from whom the name is taken. 



Within recent years doubt has arisen as to whether many of 

 the non-septate spirillary forms, e.g., Spirochete pallida, are to 

 be looked on as bacteria at all, — one view being that in, it may 

 be, many cases they represent a stage in the life-history of what 

 are really protozoa. The question is an important, one, as these 

 forms include many pathogenic agents. The ultimate classifica- 

 tion of this group of bacteria must at present be left an open 

 question, and it is convenient to denominate the non-septate 

 spiral rods Spirochastce, and those whose vital unit is a single 

 curved rod Spirilla. 



II. The Higher Bacteria. — These show advance on the lower 

 in consisting of definite filaments branched or unbranched. In 

 most cases the filaments at more or less regular intervals are 



