The interesting case reported by Barber[112] shows that there are other possibilities of food poisoning by formed bacterial poisons. Acute attacks of gastro-enteritis were produced in several individuals by the use of milk containing a poisonous substance elaborated by a white staphylococcus. This staphylococcus occurred in almost pure culture in the udder of the cow from which the milk was derived. The milk when used fresh was harmless and the poison was generated in effective quantities only when the milk stood some hours at room temperature before being used. The symptoms were similar to those usually ascribed to "ptomain poisoning." SPOILED AND DECOMPOSED FOOD There is a general belief that food is unwholesome whenever the evidence of the senses shows it to be more or less decomposed. This opinion finds expression in civilized countries in many legal enactments forbidding traffic in decomposed meats, vegetables, and fruits. There is unfortunately lack of evidence as to what kinds or degree of visible decomposition are most dangerous. In fact, some foods of high nutrient value, notably cheeses, are eaten only after somewhat extensive decomposition processes (termed ripening) have taken place. The characteristic flavors or aromas of the various hard and soft cheeses are due to the substances formed by certain species of molds and bacteria and are just as properly to be regarded as decomposition products as the unpleasant stenches generated by decomposing eggs or meat. Indeed, some of the decomposition products formed in the ripening of Brie, Camembert, or Limburger are similar to, if not identical with, those which are associated with spoiled foods. Sour milk, again, is recommended and commonly used as a food or beverage for persons in delicate health, and yet sour milk contains many millions of bacteria and their decomposition products. Some of the bacteria commonly concerned in the natural souring of milk are closely related to pathogenic types. The partial decomposition of meats and game birds is often considered to be advantageous rather than otherwise. Even eggs, a food whose "freshness" is marred for most persons by the initial stages of decomposition, are ripened in various ways by the Chinese and eaten as a delicacy after the lapse of months or years. The preserved ducks' eggs known as pidan are stored for months in a pasty mixture of tea, lime, salt, and wood ashes. "They are very different from fresh eggs. The somewhat darkened shell has numerous dark green dots on the inner membrane. Both the white and yolk are coagulated; the white is brown, more or less like coffee jelly...."[113] Increase of ammoniacal nitrogen has taken place to an extraordinary degree in these eggs, indicating much decomposition of the egg protein. The ammoniacal nitrogen in pidan is considerably higher than in the eggs known by egg candlers as black rots.