68 
D. E. SALMON. 
fiftieth, or one five-hundreth, one thousandth of a drop, we find 
that the proportion of fowls which contract the affection becomes 
continually smaller and smaller. Measuring the susceptibility of 
fowls by means of this diluted virus, we find that it varies to an 
enormous extent with different individuals. In one case a bird 
died from inoculation with one-forty-thousanth of a drop, while 
another resisted the enormous dose of one drachm, or about two 
and one-half million times the former amount. 
We will now return to our experiments in the production of 
immunity. The 2d of June, 1881, the two birds which had been 
inoculated with dilutions of 1 to 50 and 1 to 500 and recovered, 
received an inoculation with pure standard virus, while the two 
which had been inoculated with the dilutions of 1 to 2,500 and 
1 to 5,000, were tested with a dilution of 1 to 500. Not one of 
these inoculations produced the least effect; the punctures healed 
and remained free from irritation as though no virus had been in¬ 
serted, and the general health was not in the least disturbed. 
On November 7, 1881, I inoculated two fowls with a dilution 
of 1 to 2,500, two others with a dilution of 1 to 5,000, two others 
with a dilution of 1 to 10,000, and two others with the undiluted 
virus. The last two died, as did one from each of the first two 
lots. The remaining four birds had a well-marked local lesion, 
but no constitutional disturbance, and remained in the best of 
health. December 6th, all were inoculated with a dilution of 1 
to 500. This producing no effect, either general or local, they 
were reinoenlated December 13th with undiluted standard virus. 
Two now showed more or less coloration of the urates, but no 
other signs of ill health; the appetite and general appearance 
were perfect throughout the experiment. 
Ten fowls were inoculated November 28th with a dilution of 
1 to 10,000. Of these, three died, two had mild attacks and re¬ 
covered, while five had the local lesion with no general symptoms. 
December 21st, the seven birds which recovered from these 
inoculations were inoculated with the strongest virus. This was 
followed in one or two cases with yellow urates, but there was no 
loss of appetite or dulness, and all remained in excellent health. 
Up to this time more than eighty birds have been inoculated 
