Structure of the Bacteria. 3 



size between the different species, yet in absolute amount, 

 this is so slight as to require the highest powers of the 

 microscope to detect it. As an average diameter, one thirty- 

 thousandth of an inch may be taken. It is difficult to 

 comprehend such minute measurements, but if a hundred 

 individual germs could be placed side by side, their total 

 thickness would not equal that of a single sheet of paper 

 upon which this page is printed. 



Manner Of Growth. As the cell increases in size as a 

 result of growth, it elongates in one direction, and finally 

 a new cell wall is formed, dividing the so-called mother- 

 cell into two, equal-sized daughter-cells. This process of 

 cell division, known as fission, is continued until growth 

 ceases and is especially characteristic of bacteria. 



Cell Arrangement. If fission goes on in the same 

 plane continually, it results in the formation of a cell-row. 

 A coccus forming such a chain of cells is called strepto- 

 coccus (chain-coccus). If only two cells cohere, it is called a 

 diplo-coccus (twin-coccus). If the second cell division plane is 

 formed at right angles to the first, a cell surface or tetrad 

 is formed. If growth takes place in three dimensions of 

 space, a cell mass or sarcina is produced. Frequently, these 

 cell aggregates cohere so tenaciously that this arrangement 

 is of value in distinguishing different species. 



Spores. Some bacteria possess the property of forming 

 spores within the mother cell (called endospores, fig. Ig) 

 that are analogous in function to the seeds of higher plants 

 and spores of fungi. By means of these structures which 

 are endowed with greater powers of resistance than the 

 vegetating cell, the organism is able to protect itself from 

 the effect of an unfavorable environment. Many of the 

 bacilli form endospores but the cocci do not. It is these 



