The second class of ailments needs no discussion save that accorded it under the general discussions of the method of conducting the business.

The third class of ailments includes the contagious diseases.  It is now believed that most common diseases are caused by microscopic germs known as bacteria.  These germs in some manner gain entrance to the body of an animal, and, growing within the tissues, give off poisonous substances known as toxins, which produce the symptoms of the disease.  The ability to withstand disease germs varies with the particular animal and the kind of disease.  As a general rule it may be stated that disease germs cannot live in the body of a perfectly vigorous and healthy animal.  It is only when the vitality is at a low ebb, owing to unfavorable conditions or inherited weakness, that disease germs enter the body and produce disease.

The bacteria which cause disease, like other living organisms, may be killed by poisoning.  Such poisons are known as disinfectants.  If it were possible to kill the bacteria within the animal, the curing of disease would be a simple matter, but unfortunately the common chemical poisons that kill germs kill the animal also.  The only thing that can be relied upon to kill disease germs within the animal, is a counter-poison developed by the animal itself and known as anti-toxin.  Such anti-toxins can be produced artificially and are used to combat certain diseases, as diphtheria and small-pox in human beings and blackleg in cattle.  Such methods of combating poultry diseases have not been developed, and due to the small value of an individual fowl would probably not be commercially useful even if successful from a scientific standpoint.  The only available method of fighting contagious diseases of poultry is to destroy the disease germs before they enter the fowls and to remove the causes which make the fowl susceptible to the disease.

Contagious diseases of poultry may be grouped into two general classes:  First, those highly contagious; second, those contracted only by fowls that are in a weakened condition.  To the first class belong the severe epidemics, of which chicken-cholera is the most destructive.

Chicken-Cholera.

The European fowl-cholera has only been rarely identified in this country.  Other diseases similar in symptoms and effect are confused with this.  As the treatment should be similar the identification of the diseases is not essential.

Yellow or greenish-colored droppings, listless attitude, refusal of food and great thirst are the more readily observed symptoms.  The disease runs a rapid course, death resulting in about three days.  The death rate is very high.  The disease is spread by droppings and dead birds, and through feed and water.  To stamp out the disease kill or burn or bury all sick chickens, and disinfect the premises frequently and thoroughly.  A spray made of one-half gallon carbolic