48 TJmversity of California Publications in Zoology [Vol. 11 



It would be interesting to compare the haemolytie reactions 

 of the serum from fowls having epithelioma contagiosum and 

 those having roup. Our intention was to do this, but time did 

 not permit. That the fowls used for all our experiments were 

 entirely free from the effects of any former infection of either 

 epithelioma contagiosum or roup was assured by using fowLs 

 raised at the University Farm where neither disease exists. 



CONCLUSIONS 



1. Epithelioma contagiosum is a specific infectious disease. 



(a) The virus is constantly present in material from the 

 lesions found on the head and on the buccal mucous membranes, 

 and in the blood of infected fowls. The disease is readily and 

 constantly produced by inoculation with material from the lesion 

 or with the blood from infected fowls. This inoculation is not 

 the transplantation of tumor cells from one fowl to another, as 

 the virus is present in the filtrate after passage through a Berk- 

 feld filter, and so far as we are able to discover neoplasms have 

 not been produced by inoculation with such filtered extract, with 

 the exception in one case of a sarcoma of the fowl transmissible 

 by an agent separable from the tumor cells as described by Rous 

 (1911). 



(6) The period of incubation varies from three to twelve 

 days depending on the virulence of the virus and on the method 

 of inoculation. 



(c) The vii-ulence of the virus is lowered by age and by the 

 action of chemicals. Within limits the virulence of the virus 

 increases vrith passage through a fowl. 



(d) An immunity is produced, which is complete within a 

 definite time, is specific and of considerable duration. 



(e) The tissue reaction at the point of inoculation is very 

 similar to that produced by inoculation with known infectious 

 agents. 



(/) There is a definite relation between the resistance of 

 the host and the virulence of the infection, i.e., an inoculation 

 with a virus of reduced virulence produces a reaction that is 

 entirely local, while a more virulent strain produces a reaction 

 that is not limited to the point of ingress. 



