212 



TECHNICAL BULLETIN U 



the vaccinated birds did not come down with pox during tlie subsequent 

 months. 



Experiment Jf. 



Tliis experiment was planned to determine if birds after recovery from 

 natural and exjjerimental infection would react to the local or cutaneous 

 vaccination of feather follicles on the leg. A grou}) of 28 White Leghorn 

 cockerels that had recovered from contagious epithelioma was used for this 

 purpose. The control birds of the previous experiments were also used, they 

 having recovered from the experimental infection. Tiie vaccine containing 

 200 milligrams of virus in .50 cc. of a 40 per cent glycerol-piiysiological saline 

 solution was applied to the feather follicles in the manner described. 



The results v/ere clear cut. Not one bird developed a local or cutaneous 

 reaction (pox eruption) at the point of vaccination. 



Experiment 5. 



An effort was made to determine what effect the age of the cutaneous 

 vaccine of Experiments 3 and 4 had on its ability to produce a complete 

 immunity against contagious epithelioma. 



TAB E 4 — Results of ageing of the cutaneous vaccine on the subsequent production of 



complete immunity 



Iv-terpretation. The above data indicate that when the vaccine is 2.5 days, 

 or less, in age at the time it is administered, it j)roduces a complete inmmn- 

 ity. When older it does not confer absolute protection against the experi- 

 mental infection. It cannot be said at the present time wliether this attenua- 

 tion was due to actual ageing of the ^irus in tiie vaccine, the action of the. 

 glycerol upon it, or some other imsusjiected factor. Furtiier experiments arc 

 planned for determining this question. The data also show that apparently 



