4 MODERN DAIRY PRACTICE. 



of any spore-bodies within; bacillus, the normal rodlike 

 type, reproducing by spores tinder certain conditions; and 

 leptotliorix, where the filaments are extremely long and 

 slender. 



The spirilla are the curved forms, and vary most in 

 their outward appearance. They may be merely undulat- 

 ing in appearance or in segments merely curved, when they 

 are sometimes spoken of as vibrios. To this class belongs 

 the cholera germ, often called the comma bacillus on account 

 of its curved appearance. Many times the spirilla are 

 curved into several sharply-defined turns. 



Size and Weight of Bacteria. As already mentioned 

 the bacteria vary much in size, for which reason it is im- 

 possible to give their average dimensions. A couple of 

 examples will convey some idea of their extraordinary 

 minuteness. 



A common lactic-acid bacterium is generally 3 micro- 

 millimeters long and 1 micromillimeter wide. One micro- 

 millimeter (jj) is y^Vrr millimeter or 3-5 -J or f one inch. 

 How exceedingly small must not, then, the organisms be, 

 25,000 of which may be placed side by side without span- 

 ning over more than an inch ! Not less than 10,000 million 

 single bacteria would be needed to fill a cubic millimeter. 

 Their weight is also exceedingly small. If we assume that 

 the specific gravity of the bacterium mentioned is equal to 

 that of the water (this may not be exact, but is not very 

 much out of the way) it weighs a little over .0000000001 

 milligram; and something over 900 billions of such or- 

 ganisms are required to reach a weight of 1 gram (^ of an 

 ounce). 



Distribution of Bacteria. It is evident that such small 

 organisms may hide everywhere in nature. They have 



