40 MORPHOLOGY OF BACTERIA 



grow to maturity and then divide. Some of them may remain 

 linked together, and hence appear as long chains. 



In the case of the cocci, they may divide into two and remain 

 linked together as diplococci or a great many may remain connected 

 together, thus giving the appearance of a string of beads; Strepto- 

 coccus. This is the characteristic of the common blood-poison 

 organism. Other spherical shaped organisms divide alternately in 

 two planes and when they remain connected together and great 

 masses are formed they resemble a bunch of grapes; Sta'phylococcus. 

 This is a characteristic of the common boil-causing organism. Still 

 others of the spherical organisms divide alternately in three planes 

 and when they remain connected appear very similar to a bale of 

 cotton; Sarcina. This is a characteristic of many of the organisms 

 found in air. 



It has been estimated that if bacterial multiplication went on 

 unchecked, the descendants of one cell would in two days number 

 281,500,000,000, and that in three days the descendants of this 

 single cell would weigh 148,356,000 pounds. It has been further 

 estimated by an eminent biologist that if proper conditions could 

 be maintained for their life activity, in less than five days they 

 would make a mass which would completely fill as much space as 

 is occupied by all of the oceans on the earth's surface, if the water 

 has an average depth of one mile! 



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

 teria have been on this earth, and have been multiplying probably 

 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 thick, none of it will mature. Sometimes it is 

 a lack of food, other times a lack of sunshine, at still other times it 

 is a lack of moisture which prevents the growth. So it is with 

 bacteria, the food or water may give out, but more often it is the 

 products which they form that prevent them from continuing to 

 multiply. 



Brownian Movements. If one examines under a microscope a 

 suspension or colloidal solution containing particles about IM in 

 diameter, they are seen to be in motion oscillating through a dis- 

 tance about equal to their own diameter. With smaller particles 

 the oscillation is much greater proportionately. When the diameter 

 is about 4ju the motions are hardly perceptible. The mean velocity 

 for a particle of platinum weighing 2.5 x 10 ~ 15 gm. has been estimated 

 to be 3 x 10 ~ 2 cm. per second at ordinary temperature. These 

 smaller particles often travel in straight lines and suddenly change 

 their direction. Zsigmondy, describing the movement of the gold 

 particles in a gold hydrosol, compared them to a swarm of dancing 

 gnats. This interesting phenomenon is called "Brownian Move- 



