Appx. XXI.

Specimens for laboratory examination.

       As Dreyer's method of carrying out the agglutination test is in use
in all Military laboratories, collection by means of vein puncture is
practically always essential for the test to be properly carried out.

       (a ) Technique of collection in a Wright's blood capsule.—These
eapsules are obtainable on indent from Medical Store Depôts and in
emergency from the nearest military laboratory.

       Their method of use is as follows:—

       The dorsal aspect of the terminal phalanx of one of the fingers is
cleaned thoroughly with alcohol, and is pricked sufficiently deeply,
either with a bayonet pointed needle or glass pricker, to ensure a free
flow of blood. Before pricking the finger, or immediately afterwards,
a narrow bandage is wound tightly round it in such a manner as to
confine the blood in the distal phalanx.

       Both ends of the capsule are now broken off. Holding the capsule
almost horizontally and below the level of the finger, the tip of the re-
curved limb is applied to the drop of blood. This now runs in by
capillary attraction and by siphonage, the air escaping through the
straight limb of the capsule. Enough blood will have been obtained
when the capsule is two-thirds full.

       If, during the filling of the capsule, the blood ceases to flow freely
the bandage should be removed from the finger and re-applied.

       The capsule is sealed in the following manner:—A small steady
flame is employed, either the by-pass of a Bunsen burner, or if this is
not available the flame of a spirit lamp held upright. The capsule
is first slightly warmed at the junction of the body with the straight
limb, and the distal end of this tube is sealed off by holding it in the
flame. It is now allowed to cool, and in so doing the imprisoned
rarefied air contracts and the blood is drawn into the body of the
capsule, leaving the orifice of the re-curved limb free. The orifice of
this re-curved limb is now sealed up in the flame.

       The greatest care must be taken in all these operations to prevent
charring or heating the blood.

       The capsule is labelled with the patient's name and date of collection
of blood, and is packed carefully for forwarding.

       (b ) Technique of collection by means of vein puncture.—The blood
is obtained from the forearm by means of aseptic puncture of one of
the veins which have been rendered prominent by getting the patient
to clench the fist and grasp the upper arm with the other hand, or by
applying a bandage round the upper arm. A fairly large-bore hypo-
dermic needle should be employed, and at least 3 c.c. of blood with-
drawn into the syringe. This blood is now transferred to a small
test tube to allow clotting and separation of the serum. The latter
is pipetted off from the clot, sealed in a small tube and labelled with
the patient's name and date of sample.

       4. Fœces should be sent daily to the laboratory from the 8th day
of disease onwards. Specimens taken between the 10th and 21st day
of the disease are most likely to yield positive results. All specimens
should reach the laboratory within two hours after passage. When