cathartics and enemata. His attack was considered to be due to
intestinal irritation. He was not permitted, however, to return to the
camp.

No nonimmune resident was subjected to inoculation who had not passed in
this camp the full period of incubation of yellow fever, with one
exception, to be hereinafter mentioned.

For the purpose of experimentation subjects were selected as follows:
From Tent No. 2, 2 nonimmunes, and from Tent No. 5, 3 nonimmunes. Later,
1 nonimmune in Tent No. 6 was also designated for inoculation.

It should be borne in mind that at the time when these inoculations were
begun, there were only 12 nonimmune residents at Camp Lazear, and that 5
of those were selected for experiment, viz., 2 in Tent No. 2, and 3 in
Tent No. 5. Of these we succeeded in infecting 4, viz., 1 in Tent No. 2.
and 3 in Tent No. 5, each of whom developed an attack of yellow fever
within the period of incubation of this disease. The one negative
result, therefore, was in Case 2--Moran--inoculated with a mosquito on
the fifteenth day after the insect had bitten a case of yellow-fever on
the third day. Since this mosquito failed to infect Case 4, three days
after it had bitten Moran, it follows that the result could not have
been otherwise than negative in the latter case. We now know, as the
result of our observations, that in the case of an insect kept at room
temperature during the cool weather of November, fifteen or even
eighteen days would, in all probability, be too short a time to render
it capable of producing the disease.

As bearing upon the source of infection, we invite attention to the
period of time during which the subjects had been kept under rigid
quarantine, prior to successful inoculation, which was as follows: Case
1, fifteen days; Case 3, nine days; Case 4, nineteen days; Case 5,
twenty-one days. We further desire to emphasize the fact that this
epidemic of yellow fever, which affected 33.33 per cent of the nonimmune
residents of Camp Lazear, did not concern the seven nonimmunes occupying
Tents Nos, 1, 4, 6 and 7, _but was strictly limited to those individuals
who had been bitten by contaminated mosquitoes._

Nothing could point more forcibly to the source of this infection than
the order of the occurrence of events at this camp. The precision with
which the infection of the individual followed the bite of the mosquito
left nothing to be desired in order to fulfill the requirements of a
scientific exp