60 DISEASES OF POULTRY. 



these cases there may be extensive hemorrhages, either 

 locally or throughout the body, and these may con- 

 stitute the only apparent alterations. 



A microscopic examination reveals the spores or fila - 

 ments of the fungus in most of the lesions, whether 

 these are acute or chronic. The nature of the disease 

 may consequently be determined by a post-mortem ex- 

 amination, but the diagnosis is uncertain and difficult 

 during the life of the bird. 



Causation. — The various species of Aspergilli 

 which cause this disease exist abundantly in nature 

 and develop, particularly in some warm summers, 

 upon all kinds of straw and grains. When musty 

 straw or musty grain is thrown to the fowls the 

 exciting cause of the disease is placed before them. 

 As little care is exercised to remove this dust be- 

 fore straw is placed in the scratching-pens, or before 

 grain is fed, vast numbers of the spores of these parasitic 

 fungi are inhaled. This explains why the disease is 

 generally found in the air -tubes, the lungs, and the 

 air -sacs. Although many birds are exposed, but a 

 comparatively small number are affected. These are 

 probably more or less predisposed. It has been ob- 

 served, in fact, that the delicate breeds, or the delicate 

 and weak individuals, are most subject to the disease. 

 Some authors are of the opinion that colds, irritation 

 of the mucous membrane, or other forms of disease 

 generally form the starting point of this mycosis. It is, 

 also, probable that the number of spores taken into 

 the air -tubes or digestive organs has great influence in 

 determining the result. 



Prevention. ^As this disease is caused by the 

 spores of pathogenic fungi which have developed upon 



