DISEASES OF POUI.TKV. 63 



irritation of mange. Nevertheless, Holzendorff states 

 that in addition to the infection of the air -sacs he has 

 found in the lungs, liver, kidneys and other viscera, a 

 great number of yellow miliary tubercles in which he 

 also recognized this parasite. 



When the air -sac mites exist in very small numbers , no 

 signs of irritation or ill health are seen in the affected 

 birds. When they become very numerous, however, 

 they cause considerable irritation of the lining mem- 

 brane of the air -sacs and they are crowded into the 

 bronchi, where they set up inflammation, which may 

 take the form of bronchitis or broncho -pneumonia. 

 Megnin states that in such cases there may be obstruc- 

 tion of the air -passages causing fits of coughing and 

 even sudden death from suffocation. Gerlach accused 

 the Cytodites of causing enteritis (inflammation of the 

 intestines), and Zundel thought they caused both en- 

 teritis and peritonitis (inflammation of the serous 

 membrane lining the abdominal cavity). They pro- 

 bably cause anaemia, loss of flesh, and general un- 

 thriftiness, even if no form of acute disease develops. 



This parasitic affection of the air-sacs is, of course, 

 a contagious disease. The mites can not live for a very 

 long time outside of the bird's body; they are brought 

 upon a farm with affected birds and as opportunity 

 offers they pass from bird to bird until the greater part 

 or the whole of the flock becomes contaminated. No 

 doubt the mites penetrate the body by crawling into 

 the nostrils and following the trachea and bronchial 

 tubes until they reach the air -sacs. How frequently, 

 or under what circumstances they leave the air-sacs 

 and seek the outside air is unknown. 



Symptoms. — In many cases birds affected with the 



