45 



saliva, or by fibrinous exudations between the cell elements of the epithelial 



tissue. 



These two circumstances, especially the latter, produce the formation of 

 pseudo-membranes. The third, and perhaps most important, reason is that 

 the mucous membranes in the nostrils possess very many mucous cells, which 

 mix their secretion products with the transudated leucocytes, and remove these 

 from the epithelial surface. The conjunctiva, it is true, is not without mucous 

 cells; but they are relatively scarce. Pharynx and mouth are without mucous 

 cells, and. therefore, pseudo-membranes easily form in these locations. 



Besides the two bacilli already described as causing the chicken diphtheria, 

 other causal agents are more or less known ; thus, Loefifler described the 

 Bacillus diphtheriae columbarum, Loir and Ducloux, the Bacillus diphtheriae 

 gallinarum as causing diphtheria in fowls, and proved it by many experiments. 

 Besides, there are protozoa, or corpuscles similar to protozoa claimed by other 

 writers as the cause of fowl diphtheria. 



All these results show that diphtheria in fowls cannot be a specific disease 

 like the human one ; and. from this point of view, we have to consider the 

 pathological symptoms. For example, the fowl diphtheria in Tunis, as re- 

 ported by Loir and Dudoux, is differentiated from all other forms by the very 

 acute character of the disease ; the presence of the infectious germs in all or- 

 gans, secretions and excretions : and the easy infection of healthy fowls with 

 any parts of diseased ones. 



European and American fowl diphtheria is especially a chronic disease, 

 with very variable virulence, and severity of symptoms, which partly depends 

 on the causal agent. 



Roup or fowl diphtheria is generally brought into a healthy flock by a 

 diseased iowl from another place, a fowl having sufifered from a chronic attack 

 of the disease (the more common form may be a catarrh of the nostrils or 

 conchae and cella infra-orbitalis) during the summer suddenly becomes very 

 ill again during the late autumn or winter; spreads the germs of the disease and 

 infects the flock. 



The third possibility is that in unhygienic locations, fowl diphtheria may 

 appear without any preceding attack or importation of a diseased bird, the 

 causal organism being very ubiquitous, for example. B. pyocyaneus. By means 

 of the pathological secretions, the bacilli are spread throughout the whole fowl- 

 yard. These germs may become more virulent by passage through one fowl 

 to another. As the appetite is not generally altered at the commencement 

 of the disease, water and food utsenils become infected with the causal organ- 

 isms, and if these are sufficiently virulent, infection may take place by means 

 of contaminated food or water ; but in all cases which have come under our 

 observation, the first symptoms of roup generally appeared after common 

 catarrh of the mucous membranes. The roup germs, therefore, seem to be 

 unable to invade normal mucous membranes, but become a great danger to 

 those affected by common colds. Poultry keepers know very well how ex- 

 posed chickens and other fowls are to all kinds of colds by sudden changes in 



