_Polydesmus exitans_ grows on the leaves of rape and turnips, appearing in early summer. This fungus is very irritating to the mouths and feet of cattle, causing severe inflammation and the formation of a false membrane. In some instances this condition has been mistaken for foot-and-mouth disease, but it can be differentiated by the absence of the blister that is characteristic of that disease and by the further fact that it is nontransmissible. _Polytrincium trifolii_, which grows on clover, causing it to become black, causes severe irritation of the stomach and intestines of cattle feeding upon it. Feeds must not contain too large a proportion of woody fiber or of indigestible substances. If the dry matter ingested or the bulk of the feed is very great on account of the small proportion of digestible matter, it is impossible for the great mass to be moistened properly with and attacked by the digestive juices. In consequence of this, abnormal fermentations arise, causing indigestion and irritation of the digestive organs. On the other hand, a ration too concentrated, and especially too rich in protein, is not suitable, because, after a meal, the animal must have a certain feeling of fullness in order to be comfortable and quiet, and the digestive organs require a relatively large volume of contents to fill them to the point where secretion is properly stimulated and their activity is most efficient. If too much protein is in the ration there is a waste of expensive feed, and the tendency is for the animal to become thin. It is evident that a cow can not thrive on concentrated feeds alone, even though these contain in assimilable form all the nutritive materials needed for perfect support. It is because bulk is necessary that the standard of about 25 pounds of dry matter per cow per day has been reached by experimenters. There is no objection to feeding grain or meal separately to a cow, provided enough bulky feed is fed at another time in the day to keep the digestive tract sufficiently distended. In changing the ration, and especially in making radical changes, as at the beginning and the end of the pasturing season, the change should be made gradually, so that the digestive organs may accommodate themselves to it. After the digestive organs and juices have from long practice become adjusted to the digestion of a certain feed, which is then suddenly withheld and another of quite different character and properties is substituted, the second feed is not well digested; it may even irritate the digestive canal. It is often observed that cattle lose from 25 to 100 pounds when turned on pasture from dry stable feed. This loss can readily be prevented by not shocking the digestive organs by a sudden change of diet. Regularity in feeding has much to do with the utilization of the ration, and gross irregularity may cause indigestion and serious disease.