SHAPE OF MICROORGANISMS 



29 



has been shown that these bacteria which have the power of in- 

 dependent movement have on their bodies long hair-like appen- 

 dages. In some, these appendages are many times the length of 

 the body of the organisms. They may be situated at one or both 

 poles or they may even surround the entire body of the organism. 

 It is by the striking of the water with these whip-like appendages 

 that the organisms are able to move. As one examines moving 

 bacteria under the microscope one would think that they were 

 moving with the speed of an ex- 

 press train, but on actually meas- 

 uring their speed it is found to be 

 an illusion. The cholera organ- 

 ism has been known to attain for 

 a short distance the enormous 

 speed of eight inches per hour! 

 So we need not fear that they 

 will overtake even the slowest by 

 their own means of locomotion. 

 These organisms have a more 

 rapid and safer way of passing 

 from place to place. Many of 

 them use the common housefly as 



their airship, others the bedbug, while still others will chance a 

 ride with the flea. At other times they find their way into food 

 or on clothing and are transported from place to place. Some 

 are picked up with the particles of dust, but to the disease-produc- 

 ing organism this method of travel is more fatal than is the mod- 

 ern airship to man. The spore-forming organisms, however, 

 may make the journey in this manner with a fair degree of safety. 

 It is not because the fall would hurt these specks of living matter, 

 but when struck by the direct rays of the sun they are killed in a 

 very short time. Many of them cannot withstand even diffused sun- 

 light for any great length of time. Many of them could not have 

 made the journey any great distance even in the dark, for their 

 bodies are about 90 per cent water, and if not clinging to some moist 

 substance they would soon lose sufficient moisture to cause death. 



Fig. 13. — Bacteria with ilagella at one 

 pole (after Gruber). 



