ETIOLOGY 



487 



last three years this organism has not been found in the diph- 

 theritic lesions of fowls. King found a bacterium on the con- 

 junctiva of a healthy fowl that belongs to this group. Ward 

 failed to find it in his study of the disease in California. Har- 

 rison and Streit have described an organism, Bacilhis cacosmus, 

 which they consider specific. Ps. pyocyaneus has also been 

 obtained in pure culture from the exudates. Mack, who has 

 made a careful study of this disease, has failed to find any 



Fig. 113. Fowl showing eye closed. The conjunitiva is covered with 

 a thick exudate ( Ward). 



organism constantly present in the lesions. He also failed to 

 produce the disease with B. cacosmus. It is not positive, how- 

 ever, that the same disease was studied by the different writers. 

 Roup is usually introduced into a flock by the exposure 

 of the birds to sick ones at shows or by bringing affected fowls 

 on the premises. The contagion may be carried by birds 

 which have the disease in so mild a form that they show no 



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