4 BULLETIN 939, U. S. DEPARTMENT OF AGRICULTURE. 
From the data shown in the table it seems evident that as chickens 
grow older they tend to become less susceptible to infection with gape- 
worms. Apparently, therefore, the most likely reason no gapeworms 
were found among the 635 chickens from the Washington market was 
that these chickens when examined had reached an age at which they 
were no longer favorable hosts for gapeworms. Probably some of 
them had been infested earlier in life but had afterwards lost their 
parasites. How long gapeworms will persist in youhg chickens that 
do not succumb to the infestation is uncertain. That adult chickens, 
however, in those unusual cases in which they become infested with 
gapeworms. are likely to harbor the parasites only temporarily is 
indicated by some of the findings in the following experiments : 
Twelve adult chickens a year old or more were fed gapeworm 
material from cultures on April 26, 28, 30, May 2. 4, 7, 9. and 11. 
altogether receiving 8 feedings, except one which was killed May 7, 
before feeding time, and hence received only 5 feedings. Material 
from the same cultures was fed to 12 1-week-old chicks April 24. 
28, 30, May 2, and 4. All the young chickens died of gapes in 11 
to 27 days after the first feeding, and all were found infested with 
gapeworms. Except the one killed May 7, 11 days after the first feed- 
ing, the adult chickens were killed 16 to 29 days after the first 
feeding and 1 to 14 days after the last feeding. Gapeworms 
were found in only 3 out of the 12. The lungs of one killed 16 days 
after the first feeding and 1 day after the last feeding contained an 
unpaired female 2.5 mm. long, and in the trachea were two pairs, 
the females being 6.5 mm. and 10 mm. long, respectively. The 10 
mm. female was producing eggs. Another chicken that was killed 
18 days after the first feeding and 3 days after the last feeding har- 
bored in the trachea a single pair of worms. The female of this pair 
measured 13 mm. in lemrth and was depositing eggs. In the trachea 
of the third chicken, killed 29 days after the first feeding and 14 days 
after the last feeding, there were 7 dead males without females. 4 
living males without females, 3 living females with dead males. 1 
living female with a living male, and 1 living female without a male. 
The last two females contained apparently viable eggs, but in the 
other three females the eggs were apparently nonfertile, dark, and 
unnatural in appearance. All the worms, alive and dead, were firmly 
attached to the trachea. The living worms were enveloped in a thick 
layer of mucus. 
On another occasion 6 adult chickens probably a little less than a 
year old were fed with a gapeworm culture. Seven days later one 
was killed. Xo worms were found. A second chicken, killed 8 days 
after feeding, had one impaired worm, one pair of coupled worms in 
the lungs, and 14 pairs of coupled worms in the trachea, all imma- 
