8 BACTERIOLOGY. 



transparent and homogeneous substance called the 

 protoplasm, which takes up the nutriment from with- 

 out. At the periphery the protoplasm becomes denser 

 and forms what is known as the capsule of the cell. 

 The amount of protoplasm is very small, so that 

 under the microscope there appears to be only nucleus 

 and capsule. 



The morphological characters of bacteria; that 

 is, their size and shape vary greatly, and upon this 

 basis it is convenient to subdivide them, into three 

 types:- 



Mor- 



A. Coccus; plural form, Cocci. 



B. Bacillus; plural form, Bacilli. 



C. Spirillum; plural form, Spirilla. 



The cocci. are shaped like berries, that is, about 

 spherical. They may be flattened on one side or 

 concave, or split like a coffee-bean. They may be 

 arranged in pairs called diplococci; in fours, tetra- 

 cocci ; or in cubes, sarcinse. They are commonly ar- 

 ranged in long strings or chains termed streptococci, 

 or in masses, often likened to bunches of grapes, 

 staphylococci. The bacilli are rod-shaped, sometimes 

 slightly curved, and vary greatly in length, from 

 Viooo to 1 /25ooo f an mcn - They occasionally form 

 in chains or rows. The spirilla are spiral or cork- 

 screw-shaped, as the name implies. They vary both 

 in length and in the number of spirals. Of these 

 three types the bacilli are by far the most numerous 

 and the spirilla the least numerous. The types are 



