Other Intestinal Bacteria. 153 



They are seen iinder the microscope as cocci, occurring 

 as a rule in pairs, short chains, or irregular groups. They 

 do not show visible growth and do not form indol and 

 nitrite in the standard peptone and nitrate solutidns; most 

 of them do not liquefy gelatia, though occasionally forms 

 are foimd which possess this power. Until recently, no 

 systematic study of the various species found in the intes- 

 tine had been made and at present all cocci giving the 

 characteristic growth on agar and strongly fermenting 

 lactose are commonly included as "sewage streptococci." 

 Although the significance of the streptococci as sewage 

 organisms is not established with the same definiteness 

 which marks our knowledge of the colon group, these 

 forms have been isolated so frequently from polluted 

 "sources and so rarely from normal ones that it now seems 

 reasonable to regard their presence as indicative of pollu- 

 tion. Although originally reported by Laws and Andrewes 

 (Laws and Andrewes, 1894), their importance was not 

 emphasized until 1899 and 1900, when Houston (Houston, 

 1899'', 1900'') laid special stress upon the fact that strep- 

 tococci and staphylococci seem to be characteristic of 

 sewage and animal waste, the former being, in his opinion, 

 the more truly indicative of dangerous pollution, since 

 they are "readily demonstrable in waters recently polluted 

 and seemingly altogether absent from waters above sus- 

 picion of contamination." In six rivers, recently exten- 

 , sively sewage-polluted, he found streptococci in from one- 

 tenth to one ten-thousandth of a c.c. of the water examined. 



