Between the quickly perishable soft cheeses and the typical hard group, are two series of varieties, one ripened by green mold and best known by Roquefort, the other ripened by bacteria and typified by Brick cheese. These cheeses are fairly firm, hold their shape well, ripen over a period varying from a few weeks to several months and their marketable period is comparatively long. In texture they are intermediate between the conditions known as "soft" and "hard." In water-content, they range at their best from 37 to 45 percent. Outside these limits, the cheeses are often marketable but they lose in quality[63] and trueness to type. +166. The green mold group.+--There are three well-known semi-hard cheeses ripened by green or blue-green mold.[64] The mold is an incidental factor in certain other forms but none of these forms has won larger than local or purely national recognition. French Roquefort, on the contrary, is probably the most widely known of all cheeses. Stilton, to a small degree at least, has followed the English to the many lands they inhabit. Gorgonzola, although made in Italy alone, has a large market in other parts of Europe and in America. In the manipulations of manufacture, these forms are not closely related but they resemble each other in that each becomes streaked or marbled by the growth of green mold (_Penicillium Roqueforti_) through open spaces within the cheese. The "blue-veined" or marbled cheeses have a characteristic taste which is developed in its most typical form in Roquefort. +167. Roquefort cheese.+--This is a rennet cheese made from sheep's milk (with occasional and minor admixture of goat's and cow's milk) in the section of southern France centering about Roquefort in Aveyron. The practices are standardized and controlled by a few companies, thus reaching exceptional uniformity. Roquefort is uncolored, open, made from firm but brittle or crumbly, not tough or waxy curd. Each cheese is about 7¼ inches (20 cm.) in diameter and 3¼ inches (9 cm.) in thickness without a definite rind, and when ripe enough for market is scraped carefully, closely covered with tin-foil and kept in refrigerators. The cut cheese shows extensive open spaces which are lined with green mold. This cheese, in addition to a strong cheesy odor and taste, has a peppery or burning quality which according to Currie[65] is due to the formation of volatile fatty acids such as caproic, caprylic and capric from the butter-fat of the sheep's milk used. A series for Roquefort cheeses selected for excellent quality was found by Dox[66] to show the following composition: TABLE IV COMPOSITION OF ROQUEFORT CHEESE