470 INFECTION AND IMMUNITY. 



during an epidemic. The latter are a source of 

 danger as "cholera carriers." 

 characters- Typicallv the cholera vibrio is about 1.5 microns 



tics of tlie * /jr " 



organism, long and one-fourth as broad. The cells of young 

 cultures have the so-called comma shape which has 

 given the organism the name of the comma bacil- 

 lus. The form in reality is that of a segment of a 

 spiral. When two cells are attached end to end an 

 S-shape may be produced, and long spirals are 

 made up of many cells which are joined at the 

 ends. In old cultures the cells may assume the 

 form of thick rods or even appear coccus-like. The 

 vibrio possesses a single long flagellum, which is sit- 

 uated at the end. Although two, four and six flag- 

 ella have been described, Kolle states that such or- 

 ganisms are vibrios of another nature. In the 

 character and rapidity of their movement, as seen 

 in a hanging-drop, Koch compares them to a 

 swarm of mosquitoes. Old cultures may lose their 

 motility to a large extent. The cholera vibrio 

 does not form spores, although certain involution 

 forms simulate them. It stains readily with the 

 ordinary anilin dyes and is Gram negative. 

 cultivation The comma bacillus grows readily in alkaline 



from the , 



stools, culture media with characteristic appearances; it 

 is an obligate aerobe under artificial conditions, in 

 spite of the fact that it flourishes in the intes- 

 tines. The optimum temperature lies between 30 

 and 40 C. A very simple method of obtaining the 

 organism in pure culture from the stools was dis- 

 covered by Koch. In tubes of peptone bouillon 

 which have been inoculated with the feces of a 

 patient, the vibrio proliferates rapidly and within 

 a few hours exists in almost pure culture at the 

 surface of the liquid. Isolated colonies are ob- 



