46 DISEASES OF POULTRY. 



living and partially developing under such conditions. 

 The eggs may escape from the adult female worm in 

 the trachea of the bird and these eggs may hatch and 

 the embryo develop in the trachea of the same bird. 

 Hence this is a parasitic disease in which the parasites 

 may continue to develop and increase indefinitely in 

 the body of the host, after the first infection has 

 occurred. As the syngamus does not lay its eggs, 

 however, and as these are only freed by the rupture of 

 the body of the adult worm, usually after its death, the 

 most frequent course of reinfection must be through the 

 digestive organs of the bird. 



When the adult egg-bearing worms are coughed up 

 by diseased birds, these worms are eagerly seized and 

 devoured by chickens or grown fowls. In such cases, 

 while the worm is no doubt digested and destroyed in 

 the alimentary canal of the chicken, the eggs which it 

 contained are hatched and some of the embryos find their 

 way to the trachea of the bird. It is not known how 

 these embryos travel from the digestive organs to the 

 trachea. No doubt the path is a difficult and danger- 

 ous one for them; because, although there are some 

 thousands of eggs in the adult worms, ten or fifteen 

 worms have been fed to a single chicken, and, as a 

 result, not over four or five embryos would reach and 

 develop in the trachea. Probably a great many of the 

 eggs pass through the intestines and are voided with 

 the excrement before they hatch. 



The eggs, or the embryos, or both, of the syngamus 

 are undoubtedly scattered over the grounds where the 

 infested chickens run. Some of these pass through the 

 digestive organs and are scattered with the excrement 

 as just suggested; others are coughed up and out of the 

 mouth, or the adult worms may be coughed up, and 



