44 BACTEEiOLOGY. 



hundred or more cells. A thread is always cbmposed of 

 rod-shaped bacteria, bacilli, and may be compared to a row 

 of bricks in a wall. 



Micrococci multiply in like manner by division. The 

 .spherical organism is usually supposed to elongate some- 

 what just previous to fission (Fig. 8 b). The transverse 

 constriction and dividing line then appear as in the case of 

 a bacillus. According to some the micrococcus does not 

 elongate first, but divides directly into two halves. It may 

 increase in size previous to division, but its form remains 

 spherical. On the other hand the bacillus always grows in 

 length, and it would seem as if this fact could be utilized 

 in distinguishing between a true micrococcus and a very 

 short rod. 



O 



a 



Fig. 10. Division forms of micrococci, a — diplococcus, perfect form— witli 

 flattened apposed surface (gonococcus), — lanceolate form (iDneumonia); b — strepto- 

 coccus; c — Consecutive division yielding a tetrad; ^— Sarcine form resulting from 

 , division of tetrad c. e — Staphylococcus. 



The two half- spheres which result from the division of 

 micrococcus may retain this form and remain attached by 

 the undivided cell- wall. In this case the two cells are 

 spoken of as being biscuit-shaped and in pairs. The germ 

 of gonorrhea presents this characteristic appearance. 

 When micrococci grow in pairs, as in this instance, they 

 aife designated as diplococci (Fig. 10 a). 



On the other hand, as soon as the division is complete, 

 the two new cells may gradually round out and assume a 

 spherical form. They may tear apart and grow singly; or, 

 the two cells may remain attached by the narrow zone of 

 undivided cell-wall, forming thus a diplococcus. If each of 

 these two attached cells now divides in the same direction 

 as the original one, a row of four spherical organisms will 

 iresult. A continuation of this division in one direction 



