POULTRY DISEASES AND THEIR TREATMENT. I05 



lowish nodules varying from the size of a pinhead to that of a 

 pea. They may be isolated or joined together in masses of con- 

 siderable proportions. These tubercles are generally found in 

 the depth of the tissues, and even in the marrow of the bones. 

 On the mucous membrane lining the air-tubes and air-sacs, the 

 second form of disease process is seen. This consists of a 

 membranous formation, ^ of an inch or more in thickness, 

 which bears upon its surface a growth of the fungus. These 

 membranous patches are at first soft, but become firmer with 

 age, and are yellowish or greenish in color, resembling a fibrino- 

 purulent exudate. They adhere closely to the mucous membrane 

 which is there thickened and inflamed. The air-sacs are some- 

 times obstructed by these growths which may in time become 

 caseous or even calcareous. These clianges may also be seen in 

 the intestines, the mesentery, the liver and in other organs." 



"The membrane lining the air-passages may, also, be found 

 ulcerated, and the ulcers may be either naked or covered with 

 a growth of the fungus." 



"In the very acute and rapid cases, the lungs may simply 

 show inflammation, or there may be formation of pus or 

 abscesses in the lungs, kidneys, liver and spleen as in pyaemia 

 or septic infection. In some of these cases there may be exten- 

 sive hemorrhages, either locally or throughout the body, and 

 these may constitute the only apparent alterations." 



"A microscopic examination reveals the spores of filaments of 

 the fungus in most of the lesions, whether these are acute or 

 chronic. The nature of the disease may consequently be deter- 

 mined by a post-mortem examination, but the diagnosis is uncer- 

 tain and difficult during the life of the bird." 



Etiology. The disease is caused by moulds of the genus As- 

 pergillus which grow on the mucous membrane of the air pas- 

 sage. The four parasitic species in order of their importance are 

 Aspergillus fumigatuS, Aspergillus nigrescens, Aspergillus glau- 

 cus, Aspergillus candidns. The appearance of one of these 

 moulds, when greatly magnified is shown in fig. 22. 



