It is most important, therefore, to be able to recognize the symptoms and to know the causes of the many diseases to which various kinds of poultry are subject. Every practical effort should be made to reduce avoidable mortality. An unexplained death should be regarded with concern. It may point to the presence of a serious disease. When there is not sufficient external evidence for determining the cause of death, a post-mortem examination should be made (see page 98). The poultryman must know above all whether he is dealing with an infectious disease or not. The discovery that a sudden death among his fowls is due to apoplexy will set his mind at ease. On the other hand, if a case of cholera occurs, the body of the dead fowl should be burnt, and a vigorous campaign started to prevent the spread of the disease; birds showing mopishness and other suspicious symptoms should be isolated; the houses, the feed troughs, the water vessels, and the yard to which the dead fowl has had access, should all be thoroughly disinfected. _2. Dangers of Introducing Disease_ Perhaps more loss has been caused by introducing birds with disease into a healthy flock than by any other means. Readers will, doubtless, be able to recall occasions on which their own, or their neighbors’, flocks suffered. An instance was recently related to the writer. A poultryman was offered two fowls, which he at first refused, but owing to the vagrant seller’s importunity, he eventually bought the birds and let them loose among the home flock. On the following day one died; but no effort was made to discover the cause, nor was the dead fowl’s body burnt. In a few days, a fowl belonging to the original flock died and, in three to four weeks after the purchase, two-thirds of the stock had died. It afterwards transpired that the vendor had lost several of his fowls from cholera, and the fear of further mortalities had been his reason for being so anxious to dispose of the survivors. On every farm where poultry is kept, there should be a quarantine ward for new purchases. The most careful breeders will isolate their own birds that have returned from an exhibition, for fear they may have contracted some disease there or on the journey. _3. Control Measures_ Practical experience and scientific investigation have clearly proved that preventive measures are more economical and effective than curative. Failing prevention, everything points to the importance of dealing promptly with the first cases, owing to the risk of infection of the rest of the stock. Control measures may be divided into three classes: 1. Proper housing and feeding of fowls. 2. General sanitation and disinfection. 3. Administration of medicine to sick birds. The details to which special attention must be given are covered by the following axiomatic rules: 1. Isolate birds recently purchased—for two or three weeks. 2. Isolate every bird that shows any sign of ill health.