14 BACTERIOLOGY. 



The fission by which the cooci increase may take place in one 

 direction only, and if the two resulting cells remain attached to 

 each other they form a diplococous. If these two cells again divide, 

 and the resulting cells remain hnked together, we get a chain or 

 rosary, termed streptococcus. These chains may consist of a few 

 individuals linked together, or of several hundreds, in which case 

 the chains are generallj' curved or twisted. When the division 

 occurs in two directions, so that four cocci result, a tetrad or 

 merismopedia is formed ; when in three directions, one coccus divides 

 into eight, and the result is a packet form or sarcinacoccus. 

 Immediately after division, the daughter cells are not perfectly 

 circular, but are flattened or facetted where they are opposite to 



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Fig; 1.— Asoococcus Billrothii, x 65. [After Cohn.] 



each other. They gradually become rounded off, and each daughter 

 cell is then ready to divide in its turn. In other cases the cocci 

 after division only form irregular heaps or collections like bunches 

 of grapes. This form is sometimes distinguished as staphylococcus^ 

 but it cannot be considered an important feature. When we find 

 irregular masses of cocci united by intercellular substance and 

 embedded in a tough gelatinous matrix, the form is described as 

 ascococcus. 



Another type is the rod, characteristic of bacterium and bacillus. 

 The rods may vary considerably in length. The very short rods 

 with rounded ends are difficult to distinguish from the oval cocci, 

 but differ in that a rod, however short it may be, must have 

 two sides parallel. The vibrio or bent rod may be considered as 

 the connecting link between the rods and the corkscrew forms or 



