e. Sodium citrate is the anticoagulant of choice for coagulation studies. It is
used in a concentration of 1 part 0.11 M sodium citrate to 9 parts whole blood. It
prevents coagulation by binding the calcium of the blood in a soluble complex.
f. Sodium oxalate is another anticoagulant widely used in coagulation studies.
It is used in a concentration of 1 part 0.1 M sodium oxalate to 9 parts whole blood. The
sodium oxalate combines with calcium in the blood to form insoluble calcium oxalate,
thereby, preventing coagulation.
Under normal circumstances, it should not be necessary to prepare an
anticoagulant since prepared anticoagulant tubes are available through the
Federal supply system.
g. A correctly anticoagulated blood sample is essential to the proper
performance of a blood cell count. The cellular constituents must remain free in the
plasma and should be as similar as is possible to those remaining in the patient's
Section II. PREPARATION AND STAINING OF BLOOD SMEARS
a. The type of blood cells found in the peripheral blood smears may be of
diagnostic and prognostic importance. For this reason proper preparation and staining
of blood films is essential for the identification and study of different kinds of leukocytes.
The appearance of erythrocytes and thrombocytes will often give important clues that
help distinguish between different types of diseases or other physical changes.
b. There are two basic methods for the preparation of blood smears: the cover
slip and the slide methods. The cover slip method has certain advantages over the
slide method; distribution of cells is like that of the in vivo circulation. The principal
disadvantage of the latter method is that covers lips are very fragile and easily broken
c. The slides and cover glasses must be chemically clean and dry. New slides
must first be washed with soapy water and rinsed thoroughly with distilled water. The
slides are then placed in a beaker of 95 percent ethyl alcohol. As the slides are
needed, dry them with a soft, lint free cloth. The slides may be reused by properly
cleaning them and making sure they are not chipped or scratched.
d. The foundation for the morphological study of blood was based on Ehrlich's
investigations of the aniline dyes, dating back to 1877, while he was still a student.
Originally, simple dyes were used in the clinical laboratory and tissues were stained
successively if more than one color was desired. The majority of the aniline dyes are in
the form of salts of acids and bases. During the process of staining, compounds are
probably formed between the basic dyes and the acid nuclear substances of cells and