PRINCIPLES OF VETERINARY SURGERY 93 



CLASSIFICATION.— Morphologically, bacteria are di- 

 vided into Cocci or spheres; Bacilli or rods; and Spirilla or 

 screws. 



Cocci. — The coccus, or micrococcus, has a round or ovoid 

 contour, and presents several different forms of growth 

 which are subdivided into : diplococcus, when arranged in 

 pairs, streptococcus, when arranged in chains, and staphy- 

 lococcus, when arranged in clusters. When a second division 

 of the diplococcus occurs, thus making a group of four, the 

 tetracoccus is formed, and when the development continues 

 until a bale-like mass is formed the micro-organism is called 

 sarcina. Cocci are also divided into flagellated and unflagel- 

 lated, the former being a rather rare variety. 



Fig. 1. 



Various Forms of Cocci. 1, Staphylococci; 2, Streptococci; 3, Diplococci ; 



4, Tetracocci; 5, Sarcinae. 



Bacilli. — The bacilli (rods) are staff-shaped or rod- 

 shaped, and consist of elongated cells. They vary greatly in 

 shape, from elliptical forms to long slender threads, and in 

 size, from very small to very large bacteria. Some have 

 rounded extremities and others square ones. They divide 

 by transverse fission. There are both flagellated and lui- 

 flaggellated varieties. 



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Fig. 2. 

 Forms of Bacilli. 1, Single Bacilli ; 2, Bacilli in Pairs ; 3 Bacilli in Threads. 



