There is also a certain amount of offensive dirty matter which may fall into the milk-pail, and carry with it undesirable germs. These impurities may, to a certain extent, be eliminated by good straining, but a surer prevention is to have the cow-house perfectly clean and free from dust, as dust specks are in many cases the vehicles of disease germs. Cleanliness is, in fact, the essential feature in modern dairying, not only in the cow-house, but in the milking utensils, the drainage, etc., and, above all, the milker should be of cleanly habits. The flavours of milk sometimes arise from the absorption of evil-smelling gases in the cow-house, or from a peculiar taint from certain roots and feeding stuffs, and in such a case it is desirable that aëration should take place in a fresh clear atmosphere, so that oxygenation may have the effect of eliminating and destroying the foreign odours and flavours which may be present. If this process of aëration is carried out at blood heat, the result is generally highly satisfactory. _Milk Management._—There have been many excellent tables of rules published for the management of dairies in different countries, but they are necessarily framed within certain limitations which apply to all. The following is an excellent set, which put concisely the conditions necessary to be observed in the modern cow-house: 1. The cow should be sound—no disease should exist in the animal. 2. The feed should be good and free from aromatic substances. If these aromatic foods are used, they should be employed according to those methods which will not cause odours or flavours to appear in the milk. 3. The cow should be groomed, and hair about the udder preferably clipped. 4. The udder should be moistened during milking. 5. The milker should be a neat, tidy person. 6. The milker should be free from disease, and should not come in contact with any communicable disease. 7. The milker's clothes and hands should be clean while milking. 8. The pail should be sterilised. 9. The stall should be such as to reduce the amount of disturbance of dust and dirt. 10. There should be good light, good ventilation, and good drainage in the cow-house. 11. The cow-house should always be kept clean. 12. Feeding and bedding, unless moist, should be done after milking. 13. A dustless milking-room is desirable. 14. Milk should not stand in the cow-house. 15. If milk is aërated, it should be done before cooling and in pure air. 16. The sooner the milk is cooled after milking the better. 17. Keep the milk as cold as possible when once cooled.[45]