30 Structure and Classification of Micro-organisms 



1. Spirosoma. Rigid; without flagella. 



2. Microspira. Rigid; having one, two, or three undulating flagella 



at the ends. 



3. Spirillum. Rigid; having from five to twenty curved or undulat- 



ing flagella at the ends. 



4. Spiroch&ta.* Serpentine and flexible. Flagella not observed; 



probably swim by means of an undulating membrane. 



B. SUB-ORDER: Trichobacteria (Higher Bacteria) 



IV. Family MYCOBACTERIACE^. Cells forming long or short cylindric 

 filaments, often clavate-cuneate or irregular in form, and at times 

 showing true or false branchings. No endospores, but formation of 

 gonidia-like bodies due to segmentation of the cells. No flagella. 

 Division at right angles to the axis of rod in filament. Filaments not 

 surrounded by a sheath as in Chlamydobacteriaceae. 



1. Mycobacterium. Cells in their ordinary form, short cylindric 



rods often bent and irregularly cuneate. At times Y-shaped 

 forms or longer filaments with true branchings may produce 

 short coccoid elements, perhaps gonidia. (This genus includes 

 the Corynebacterium of Lehmann-Neumann.) No flagella. 



2. Aclinomyces. Cells in their ordinary form as long branched fila- 



ments; growth coherent, dry or crumpled. Produce gonidia- 

 like bodies. Cultures generally have a moldy appearance, due 

 to the development of aerial hyphae. No flagella. 



V. Family CHLAMYDOBACTERIACEAE. Forms that vary in different stages 

 of their development, but all characterized by a surrounding sheath 

 about both branched and unbranched threads. Division transverse 

 to the length of the filaments. 



1. Cladothrix. Characterized by pseudo-dichotomous branchings. 



Division only transverse. Multiplication by the separation of 

 whole branches. Transplantation by means of polar flagellated 

 swarm-spores. 



2. Crenothrix. Cells united to form unbranched threads which in 



the beginning divide transversely. Later the cells divide in all 

 three directions of space. The products of final division become 

 spheric, and serve as reproductive elements. 



3. Phragmidiothrix. Cells at first united into unbranched threads. 



Divide in three directions of space. Late in the development, 

 by the growth of certain of the cells through the delicate, closely 

 approximated sheath, branched forms are produced. 



4. Thiothrix. Unbranched cells inclosed in a delicate sheath. Non- 



motile. Division in one direction of space. Cells contain sulphur 

 grains. 



II. ORDER: THIOBACTERIA (Sulphur Bacteria) 



I. Family BEGGIATOACE^E. Cells united to form threads which are not 

 surrounded by an inclosing sheath. The septa are scarcely visible. 

 Divide in one direction of space only. Motility accomplished through 

 the presence of an undulating membrane. Cells contain sulphur 

 grains. 

 There are two families, numerous sub-families, and thirteen genera in this 



order. They are all micro-organisms of the water and soil, and have no 



interest for the medical student. 



Structure. Nucleus. When subjected to the action of nuclear 

 stains, large vague nuclear formations are usually observed in the 

 bacterial cells, f 



* The spirochseta and some closely related forms are now thought to be 

 more properly classified among the protozoa than among the bacteria. They 

 will, therefore, appear again in the tabulation of the protozoan organisms. 



t For literature upon the nucleus of the bacteria, see the lengthy paper by 

 Douglas and Distaso ("Centralbl. fur Bakt.," etc., I. Abt. Orig., LXVI, p. 321). 



