In addition to the abnormalities due to gas, there are also other faulty types. The following chromogenic conditions occur: _red cheese_, due to a micrococcus; _blue cheese_, produced, according to Vries, by a bacillus; and _black cheese_, caused by a copious growth of low fungi. _Bitter cheese_ is the result of the _Micrococcus casei amari_ of Freudenreich, a closely allied form of Conn's micrococcus of bitter milk. Sometimes cheese undergoes a putrefactive decomposition, and becomes more or less putrid. These latter conditions, like the gassy cheeses, are due to the intrusion of bacteria from without, or from udder disease of the cow. Healthy cows, clean milking, and the introduction of pure cultures are the methods to be adopted for avoiding "diseases" of cheese and obtaining a well-flavoured article which will keep. Finally, we may quote five conclusions from the prolonged researches of Mr. Lloyd[70] which cannot but prove helpful to the Cheddar cheese industry in England: 1. To make Cheddar cheese of excellent quality, the _Bacillus acidi lactici_ alone is necessary; other germs will tend to make the work more rather than less difficult. Hence scrupulous cleanliness should be a primary consideration of the cheese-maker. 2. No matter what system of manufacture be adopted, two things are necessary. One is that the whey be separated from the curd, so that when the curd is ground it shall contain not less than 40 per cent. of water, and not more than 43 per cent.; the other point is that the whey left in the curd shall contain, developed in it before the curd is put in the press, at least 1 per cent. of lactic acid if the cheese is required for sale within four months, and not less than 8 per cent. of lactic acid if the cheese is to be kept ripening for a longer period. 3. The quality of the cheeses will vary with the quality of the milk from which they have been made, and proportionately to the amount of fat present in that milk. 4. "Spongy curd" is produced by at least five organisms, and one of these is responsible for a disagreeable taint found in curd. They occur in water. Hence the desirability of securing clean water for all manipulative purposes, and also for the drinking purposes of the milch cow. 5. The fact that certain bacteria are found in certain localities and dairies is due more to local conditions than to climatic causes. It is needless to remark that these conclusions once more emphasise the fact that strict and continual cleanliness is the one desideratum for bacteriologically good dairying. That being secured in the cow at the milking, in the transit, and at the dairy, it is a comparatively simple step, by means of pasteurisation and the use of good pure cultures of flavouring bacteria, to the successful application of bacteriology to dairy produce. _Methods of Examination of Milk_: