The organisms ordinarily classed as S. lacticus (or Bact. lactis acidi) represent a group that is extremely important in the field of dairying. Altho they are responsible for a great deal of loss, since they are the principal type that sours milk and cream and thus spoils for certain purposes large quantities of these materials, they are ordinarily classed as the desirable lactic acid bacteria because of the role they play in the making of certain dairy products.