34 V niversity of California Publications in Zoologij [Vol. 11 



removed or falls off leaving a core of granulation tissue. This 

 core soon shrivels and disappears, leaving little or no scar. 



Intravenous Inoculation. — When inoculation is by intravenous 

 injection, the period of incubation is greatly lengthened, but 

 otherwise the clinical course is unchanged. 



Mucous Membrane Inoculation. — If the mucous membranes 

 of the mouth be inoculated small spongy masses form at the point 

 of inoculation. These break dowTi to form cheesy masses (prob 

 ably from secondary infection) and in some measure resemble 

 the membrane of diphtheria. In about one half our cases these 

 patches appeared on the mucous membranes of the mouth and 

 throat following an inoculation by scarification of the comb, al- 

 though the mucous membranes were left entirelj' intact in the 

 operation. In about an equal number of cases the disease ran 

 its entire course without the mucous membranes showing any 

 change whatever (inoculation being by scarification of the comb 

 and wattles). 



Eelationship of Virulence of Virus to Resistence of Host. — 

 It would seem that the occurrence of lesions is, or is not limited 

 to the point of inoculation Ijy tlie relation wliich exists between 

 the resistance of the host and the virulence of the virus used. 

 Naturally such a relationship is difficult to determine, but our 

 results are at least strongly suggestive of its existence. If a 

 small amount of a weakened virus was used and the area of sacrifi- 

 cation was small, the lesion produced did not spread beyond the 

 original area of scarification, and remained small throughout the 

 course of the disease which was somewhat shortened. If a large 

 amount of the same weakened virus was used, but the area scari- 

 fied was large, a large growth was produced, although in no case 

 was a growth noted except at the seat of the original inoculation. 

 When the infective agent has a lowered virulence the period of 

 incubation is prolonged, the manifestation of the disease is limited 

 entirety to the site of ingress, the course of the disease may be 

 shortened, and there is no clinical evidence of any general con- 

 stitutional effect except an immunity to further infection with 

 the same agent. It seems that this observation is of considerable 

 importance in determining the nature of the disease and must be 

 taken as a strong reason for believing epithelioma contagiosum 

 to be an infectious disease. 



