44 BACTERIOLOGY, 



strepto- The streptococcus is one of the pus-forming cocci 



COCCUS I 1 



pyogenes that is characterized by multiplication in one plane, 

 producing strings or chains of cocci. (See Fig. i, A, 

 3, page 7.) There are numerous varieties of strepto- 

 cocci that differ in size, shape, and virulence. They 

 may be found in water, milk, dust, and discharges 

 from the intestinal tract. In general they are more re- 

 sistant to harmful influences than the staphylococci, 

 and more virulent ; consequently infections due to them 

 are more serious and attended with a higher mor- 

 tality rate. The toxic symptoms, fever, rigors, sweats, 

 and so o>n, are more pronounced. 



Infections with the streptococcus may be localized 

 as in the case of boils, abscesses, and carbuncles; but 

 because of the greater virulence, they are liable to 

 cause edema and to extend along the lymphatic vessels 

 to involve the adjacent lymphatic glands. In the lungs 

 the streptococcus frequently causes pneumonia and 

 empyema; in the throat, tonsillitis with the formation 

 of a membrane often identical with that seen in diph- 

 theria, and, in the skin, erysipelas. It is often the 

 infecting agent in disease of the bones, osteomyelitis, 

 and in the general infections such as endocarditis and 

 puerperal fever. In association with other bacteria 

 they gave rise to what are called mixed infections, 

 coccus The Micrococcus tetragcnus is a pus-forming 



tet nuf e " organism of low-grade virulence. Its arrangement is 

 peculiar, forming squares of four cocci. It is found 

 frequently in the sputum and causes infection usually 

 in combination with some other micro-organism. 



