SHAPE OF MICROORGANISMS 



27 



Even in the face of these assumptions one need not fear, for 

 bacteria have been on this earth, and have been multiplying, prob- 

 ably long before the advent of man, and as yet the earth has not 

 been filled by them. This is due to there being a struggle among 

 them just as there is among higher plants and animals. One 

 knows that if wheat be sown too thickly, none of it will mature. 

 Sometimes it is due to a lack of food, other times to a lack of 





f ' 



f C 



^^ J 



O 



J 



r 



\ 



v*%, 



{. 



Fig. 10. — Small Spirilla (after Ome- 

 lianskl). 



Fig. II. — Involution forms of bacilli 

 (after Harrison). 



sunshine, and at still other times it is due to a lack of moisture 

 which prevents its growth. So it is with bacteria — the food or 

 water may give out. However, more often it is the bacterial 

 products which have accumulated to such an extent that their 

 multiplication is prevented. 



Size and Weight. — The unit of measurement in microscopic 

 work is the micron. It is one-thousandth of a millimeter in 

 length, or approximately one-twenty-five-thousandth of an inch. 

 It is represented by the symbol [^. Most bacteria are from 0.5 to 5 

 microns in length. Some are so small that they cannot be seen 

 with the microscope. Others may be even thirty or forty microns 

 in length. They are smallest in the case of the cocci and largest 

 in the case of the spirilla. 



Although there is a great variation in the size of bacteria, all 



