CUTANEOUS VACCINE FOR FOWL POX 239 



number of follicles was vaccinated, never less than three or more than ten. 

 This was done for the purpose of comparing the nunilber of follicles impli- 

 cated in the vaccine reaction with the effect on the bird. 



All the birds were examined periodically after the treatment. In some 

 of the more crowded pens small diphtheritic patches, rarely larger than the 

 head of a pin, developed on the mucosa of tile mouth in abo^t 5 to 10 per 

 cent of the birds. In some pens 2 to 3 per cent of the birds showed small 

 pox nodules on the comb and eyelids. These lesions developed about four 

 or five days after the treatment and disappeared within the next seven days. 

 They were regarded as of negligible importance. These lesions developed 

 within the usual incubation period of the disease and were permitted to do 

 so because of the fact that cutaneous immunity in fowl pox, as demonstrated 

 in our previous work (3), does nut begin to develop definitely until the 

 twentieth day after vaccination, becoming complete on the twenty-ninth to 

 thirty-first day. 



With the exception of the slight lesion cases which developed soon after • 

 the vaccination, there has not been one case of fowl pox or avian diphtheria 

 in this flock since the treatment. Furthermore, colds and roup have been 

 practically absent. This latter fact is interesting, but by no means con- 

 clusive evidence that cutaneous vaccination protects against colds and roup 

 as well as fowl pox. With outbreaks of fowl pox occurring on this plant 

 annually for the previous four years, one would expect it to recur the fifth 

 year. 



Two or tiiree months after this flock was vaccinated it was accidentally 

 subjected to natural infection. A group of 60 White Leghorn cockerels had 

 been quartered in a fenced-in enclosure on the premises. These birds were 

 not vaccinated because they were a reserve group from which birdsi were 

 to be taken for indicatory experiments. The natural infection appeared in 

 these birds, and some escaped through the fence, exposing the vaccinated 

 birds to the infection. Lesions of the disease did not appear in the vac-" 

 cinated birds as a result of this exposure to the natural infection. 



It was impossible to control the work properly by leaving unvaccinated 

 birds in the various pens. The flock is an important one because of the varied 

 uses made of it. It must be kept in the best of condition, and it was feared 

 that unvaccinated birds would come down with the infection later on and 

 seriously interfere with the flock program. 



A careful analysis was made of the egg production of all vaccinated 

 birds. Many of the pullets were laying at the time that they were vac- 

 cinated; some pens laying as high as 10 per cent. Several feeding experi- 

 ments were being carried on at the same time and the birds were being 

 constantly handled for student instruction. Production records of unvac- 

 cinated controls were not available. Therefore, a complete and accurate 

 summary of the effect of vaccination on this early egg production could 

 not be made. The results, however, to some degree were comparable to 

 that of flock 2. 



Flock 2. 



This flock is maintained by the Agricultural Experiment Station for its 

 work in genetics. It had been affected by annual outbreaks of potx, diph- 

 theria, colds, and roup and had been treated similarly to flock 1. In the 



