MORPHOLOGY OF BACTERIA 23 



ness of the bacteria. If they are represented by tiny cubes, 

 a micron on each edge, one billion of them would be con- 

 tained in a cubic millimeter, and one thousand billion in a 

 cubic centimeter. If a sample of milk contains a billion 

 bacteria per cubic centimeter, it means that less than one 

 thousandth of its volume consists of bacteria. 



Ultramicroscopic organisms. It is known that there are 

 forms of life so small that they are invisible under the 

 highest powers of the microscope. An object having a di- 

 mension loss than 0.2 micron can not be demonstrated by 

 the microscope. The term ultramicroscopic organism is 

 applied to such. The proof of their existence lies in the 

 fact that an animal can be inoculated with a minute quan- 

 tity of the blood of another animal suffering from some 

 one of certain diseases. The presence of organisms in the 

 blood injected can not be demonstrated microscopically. 

 The inoculated animal acquires the disease. From it 

 another animal can be inoculated. The process can be 

 extended through as long a series as is desired, with con- 

 stant results, which can be explained only by the presence 

 of a living organism in the original material used. Only 

 a living form could thus perpetuate itself. The term 

 filterable virus is also applied to such minute organisms, 

 for the reason that they pass through filters that remove 

 the bacteria. 



One gains some conception of the size of atoms and mole- 

 cules when it is recognized that in each of these minute 

 organisms there are many different chemical substances, 

 and many molecules of each. Chemical processes and trans- 

 formation of energy, that man can not and probably never 

 will be able to duplicate, since they represent the life pro- 

 cess, the power of self-perpetuation, are going on in each 

 minute cell. 



Higher bacteria, Between the various typical groups 



