78 VETERINARY BACTERIOLOGY 



the name Diplococcus is sometimes applied. This has been used 

 by some writers as a genus name. 



Micrococcus. All spherical organisms the cells of which do 

 not occur either in chains or packets are generally included under 

 the genus name Micrococcus. As defined by Migula, the name 

 strictly applies only to those organisms which divide alternately 

 in two planes at right angles to each other, forming pairs and 



Fig. 41. Types of Streptococci: a, d, Streptococci consisting of uniform ele- 

 ments; 6, Streptococcus consisting of diplococcus elements; c, Diplococcus. 



fours and. eventually a plate. Very few bacteria develop in this 

 manner. It has been assumed by some authors that division 

 may occur in the two planes, but the cells may divide at such 

 irregular intervals that irregular masses of the organisms may 

 be formed. It is altogether probable that some of the cocci 

 divide irregularly and not in planes strictly perpendicular or 

 parallel to previous planes of division. This results in the forma- 



ooof 



Fig. 42. Types of Micrococcus: a, Micrococcus of isolated cells; 6, Micro- 

 coccus showing tetrads, forming plates of cells or merismopedia; c, Micrococcus 

 with cells in an irregular mass Staphylococcus. 



tion of irregular groups. When the organisms remain united, as 

 frequently occurs, they form irregular bunches, to which the name 

 Staphylococcus is sometimes given. As used in the following chap- 

 ters, the term Staphylococcus is synonymous with Micrococcus. 



Bacillus. As used here, the term Bacillus includes all rod- 

 shaped organisms. Two other names are used by some authors, 

 namely, Bacterium and Pseudomonas. Bacterium is defined by 

 some authors as a non-motile bacillus, by others as a non-spore- 



