COCCACE^ AND THEIR PARASITIC RELATIONSHIPS 275 



animals has a marked protective influence when injected into 

 animals and has been employed in treating human infections, 

 in some cases with success, while in others the serum has appar- 

 ently exerted no influence on the course of the disease. In local- 

 ized chronic streptococcus infections, treatment with autogenous 

 bacterial vaccines (bacteria suspended in salt solution and killed 

 by heat) seems to produce favorable effects in some cases. 



Streptococcus Lacticus (Micrococcus Ovalis). — This is a 

 variety of streptococcus growing normally in the intestine and 

 of special importance as the cause of the normal souring of milk. 



The classification of the streptococci has been studied exten- 

 sively in recent years. The fermentative effects upon blood and 

 upon various sugars, especially lactose and mannite, are important 

 criteria. The advanced student should consult the article of 

 Blake^ and the monograph of Brown, ^ both of which give refer- 

 ences to the hterature. 



Staphylococcus (Micrococcus) Atu'eus. — By the early ob- 

 servers (Rindfleisch, Klebs) this organism was not distinguished 

 from the streptococcus. Pasteur in 1880 obtained it in broth 

 cultures from pus. Ogston in 1882 clearly distinguished it from 

 the streptococcus. Rosenbach (1884) by his extensiye inves- 

 tigations established the position of the staphylococcus as a 

 cause of wound infection and of osteomyelitis. 



Staphylococci have their natural habitat on the skin, in the 

 mouth, in the nasal cavities and in the intestine, without the 

 presence of inflammation. More virulent forms occur in in- 

 fected wounds, furuncles, carbuncles, various localized purulent 

 inflammations, bacteremia (staphylococcemia), endocarditis, 

 osteomyeHtis, meningitis and pneumonia. 



The cell is spherical, 0.7 to o.q^u in diameter. Division takes 

 place in various planes, giving rise to irregular bunches of cocci. 

 The organism stains readily and is Gram-positive. Cultures 



' Blake, F. G., Journ. Med. Rsch., 1917, 36, p. 99. 



" Brown, J. H., Monographs of the Rockefeller Institute for Medical Research, 

 No. 9, 1918. 



