culture to insure the proper control of the process. The amount of acid already present when the rennet is added affects not only the texture of the curd as first found, but within limits indicates also the rate at which further acidity may be expected to develop. A series of experiments in making Roquefort were tabulated to show the rate of acidification from various initial points. In the graphs (Fig. 8) the curves for acid development are parallel after the determination reaches 0.30 per cent. These experiments were made at a temperature 80° to 84° F. Milk at the lowest acidities tried developed titratable acid very slowly. A period of several hours was required to produce sufficient acid to affect the curd texture. When the acid reached 0.25 per cent by titration, the further rise was rapid and all the lines became almost straight and parallel after the titration reached 0.30 per cent. If this rapid souring occurred after the completion of the cheese-making process, the texture of the experimental cheese was not measurably affected. In those cases, however, in which 0.30 per cent was reached before the cheese reached its final form in the hoop, the texture of the ripened cheese was entirely different from that desired for this variety under experiment. These curves apply directly to but one cheese process in which a particular combination of acidity, rennet and time is used to obtain a very delicately balanced result. In other varieties it is equally important to obtain exactly the adjustment of these factors which will bring the desired result. [Illustration: FIG. 8.--The acidification of Roquefort cheese.] +80. Acidity of milk when received.+--If proper care has been taken, milk should be delivered to the factory fresh, clean and without the development of acid. If the milk has not been handled properly, the early stages of souring or some other unfavorable fermentation will have developed. Such milk may develop too much acid, or gas, or any one of several objectionable flavors during the making and ripening of the cheese. Some cheese-makers become very expert in detecting the first traces of objectionable qualities, but most makers are dependent on standardized tests to determine whether milk shall be accepted or rejected, and when accepted to determine the rate at which it may be expected to respond during the cheese-making process. Various tests have been devised to determine the amount of acid present in milk. There are two tests commonly used in cheese-factories. One is known as the "acid test" and the other the "rennet test."