162 
Dourine 
marked by a file or pencil, and expelling it into the abdomen, repeating 
the process with the same pipette for each rat. The object is to have all 
the rats come down together with a heavy infection. In the ordinary 
course a white rat dies of dourine between the end of the third and the 
beginning of the fifth day of infection. When twenty-five rats are 
inoculated at the same time about fifteen of them show a heavy try¬ 
panosome infection at the end of the third day, the remainder within 
the next 12-24 hours. It is necessary to make a rapid cover-glass 
examination of the blood of each rat forty-eight hours or so after inocu¬ 
lation and to sort the animals according as they show a light or a heavy 
infection into two or more groups. The result of the first blood examina¬ 
tion will indicate approximately the time for a second examination and 
upon that the hour for bleeding may be judged. The timing of this 
operation is important for in the last six or eight hours of infection the 
trypanosomes multiply enormously, and if the rats are left until well 
on into this stage a very rich antigen will be furnished. Careful timing, 
however, is necessary, for it may easily happen that eight or ten rats 
will all die within one to two hours, if left too long. The bleeding 
should be carried out as rapidly as possible. The writer’s method is 
simple and effective and may be worth describing in detail: 
A running noose is made out of a two-foot length of thin copper 
wire, doubled over in the middle and twisted to the ends, the ends 
being passed through the ring formed at the beginning of the twist to 
form the noose and attached to any convenient fixture over a laboratory 
wash basin, six inches above an operating board resting across the basin. 
An ether jar, a flask of citrated salt solution, two sterile covered beakers 
and a razor complete the outfit. 
An assistant passes the rats one at a time into the ether jar and 
hands them over as required. The animal is held back downwards in 
the left hand of the operator whose index or middle finger presses on 
the left front limb of the rat. The noose is slipped over the head and 
arranged so that the pull stretches the left side of the neck bending the 
head slightly to the opposite side, backwards and downwards. A beaker 
half filled with citrated salt solution is placed in position under the neck, 
the arteries and veins on that side and close to the shoulder then severed 
with a single sweep of the razor. Usually, the animals bleed better if 
one avoids severing the trachea. In this way ten rats may be bled in 
half-an-hour. The volume of blood and citrated salt solution should 
be about equal or a slight excess of the latter. The mixture is then 
passed through a double layer of sterile gauze to remove any small 
