FOURTEENTH ANNUAL YEAR BOOK— PART X. 725 



from the others. The treatment applicable to one is equally applica- 

 ble to the others. For the practical purpose of combating them in the 

 poultry yard we may therefore group these diseases together. 



Causation. — There are certain germs (bacteria) which are nearly 

 always found in the intestines of healthy fowls which have more or 

 less power to produce disease, but which the sound, healthy fowl is 

 able to resist under favorable conditions. If these germs are inocu- 

 lated into canary birds, they produce a fatal disease, because the 

 canary does not have the power to resist them. If inoculated from 

 one canary to another three or four times, these germs have their 

 disease-producing powers so increased that they are able to kill adult 

 fowls. When the resisting powers of fowls are diminished by expo- 

 sure to cold, hunger, thirst, and exhaustion, as occurs during long 

 shipments by rail, these germs may also cause disease in the fowls. 

 In some countries the sickness which develops from these conditions 

 is called "the transportation disease." 



It sometimes happens that this disease develops in poultry yards 

 which are not kept clean, possibly because of the large numbers of 

 these germs which are taken into the bodies of the birds, but probably 

 because they have acquired greater disease-producing powers from 

 growing in warm manure. When they begin growing in the tissues 

 of fowls they soon increase their virulence, and the disease which 

 they cause may rapidly spread from fowl to fowl until the greater 

 part of the birds are dead. 



The typical germ of fowl cholera has adapted itself more completely 

 than have these common germs to the conditions of life within the 

 fowl's body, so that it is strictly parasitic, and is only obtained from 

 fowls which are affected or have been affected with the disease. That 

 is, birds only contract true fowl cholera by exposure to contagion that 

 originates in other birds that have or have had the disease. 



The cholera-like diseases may, therefore, either develop in the poultry 

 yard from insanitary conditions, or they may be introduced by con- 

 tagion carried by new birds which are added to the flock, by birds which 

 have been to exhibitions, by wild birds which fly from one poultry yard to 

 another, or by various animals, such as dogs, cats, rats, etc. Birds 

 which recover from the disease may sometimes carry the germs and 

 disseminate the contagion for six months or a year after they are 

 apparently well. 



Symptoms. — The first symptom is a yellowish coloration of that 

 part of the excrement which is secreted by the kidneys and which in 

 health is nearly or perfectly white. Soon there is diarrhea, the drop- 

 pings consisting of the whitish or yellowish secretions of the kidneys 

 mixed with considerable thin mucus and a small quantity of intestinal 

 contents which may have a yellowish, brownish, or greenish color. 

 There is considerable fever, and soon after the bird is attacked it loses 

 its lively appearance, separates, itself from the flock, and appears dull, 

 dejected, and sleepy. It no longer searches for food, but sits with the 

 head drawn down to the body or turned backward and resting in the 

 feathers about the wing. The plumage soon loses its brilliance, the wings 



