DISEASES OF POULTRY. 217 



founded together by modern writers under the general 

 name of roup, one of- the most prevalent and destruc- 

 tive is the diphtheria of birds, or diphtheritic roup. 

 While some writers are of the opinion that contagious 

 catarrh and diphtheria are caused by the same species 

 of bacillus, differing only in the degree of virulence, 

 the fact that in extensive outbreaks of the former 

 disease there are apparently no diphtheritic membranes 

 to be found, bears strongly against this theory and 

 makes it desirable, at least for the present, to describe 

 these different forms of disease separately. 



The diphtheria of birds is a contagious disease 

 which first affects the mucous membrane of the nasal 

 passages, the eyes, the mouth, the pharynx and 

 larynx and which may extend to the trachea, the 

 bronchi, the air -sacs, the intestines and perhaps to 

 other abdominal organs. The disease is characterized 

 by a grayish -yellow fibrinous exudate, called a y«te 

 membrane, which forms upon the mucous surface of 

 the parts mentioned. This exudate is intimately 

 attached to the living tissues, so that when it is 

 forcibly removed a raw, bleeding surface may be left. 

 Its formation may be so abundant as to obstruct the 

 passages through which the air is drawn into the 

 lungs. The appearance of the diseased parts bears a 

 close resemblance to what is seen in human diphtheria, 

 but the bacillus which is believed to cause avian 

 diphtheria is quite distinct from that which causes the 

 disease in children, and it is, therefore, concluded that 

 the diphtheria of mankind and that of birds are 

 entirely different diseases. There are some striking 

 cases on record, however, which indicate that the 

 diphtheria of fowls may be communicated to children 

 in some instances and cause a serious or even fatal 



