148 



POULTRY DISEASES 



or even much larger. It may be accompanied by 

 roup ; in fact, we have studied both diseases in th« 

 same floclc, an occurrence which is not uncommon. 

 The question naturally arises, are both due to fil- 

 terable viruses (germs so small that they pass 

 through porcelain filters, and too small to be seen 

 through a microscope), and are both present in 



Fig. 46. Chicken Pox 

 A, Epithelial, tumor-like nodules. ]j, an ulcer. 



the same outbreak, or are both due to the same 



cause? At the present time there are conflicting 



reports by scientific men. Fig. 46 illustrates a 



case of this disease. 



One investigator has reported that immunity 



against ehickenpox does not confer immunity to 



roup. 



Harlng and Kofoid have shown that there is a specific 

 antibody developed in birds affected with ehickenpox. By 



