General Remarks and Definitions
Blood cells may be studied in a variety of ways. A perusal of the literature sometimes gives the impression that one technical method is far superior to another+ADs- but actually each method has its particular merit, and it is often found that the advantages of a different approach compensate for the shortcoming of the method that has been selected as the one generally to be followed.
Some of the principal methods for studying blood and some of the advantages and disadvantages that have been claimed for each method are listed in table 1. The method chosen for this Atlas is the air-dried smear. It was chosen for the reasons given in table 1 and because it is the method most commonly used for routine blood examination.
Wright's stain was employed for the circu+00A- lating blood because it is the stain that is most familiar to a large number of veterinarians and research workers who are not specialists in the field of blood. Other stains would undoubtedly have made it possible to carry out certain phrases of the study with greater precision, but Wright's stain, in solution, keeps well, is easy to apply, and may be procured from any medical or bio+00A- logical supply house.
|Method of study||Advantages||Disadvantages|
1. This method permits a great variety of|
technics to bring various components and
reactions of cells into view. Many technics
can be used that are sufficiently specific to
be microchemical tests.
1. Considerable alteration occurs in the trans-|
sition from life to death+ADs- thus it becomes
difficult to distinguish between structures
that existed in life and artifacts brought
about by death.
1.Tissue, fixed, sectioned, and
An example would be to drop a piece
of tissue such as embryo spleen in
Zenker formol, wash, run through
alcohols, embed, section, and stain
in hematoxylin and azure II eosin.
1. Cells are fixed approximately their|
normal shape+ADs- that is, they are not flattened
as in dry smears.
2. Maintains topographic relationship of cells|
so that daughter cells and clusters of cells
having a common ancestor can be identified
by their proximity.
3. Shows fixed cells of tissue as well as blood|
4. Some regard the cytological appearance|
of fixed and sectioned blood cells as more
reliable than smears for distinguishing
1. Cells are not killed as quickly in the center|
of a mass of tissue as they are in a smear, so
that alterations in shape and organization
2. The method is time consuming, especially|
if a celloidin technic is employed. This im+00A-
poses a greater limitation on a survey type of
study than does the smear method.
3. Most investigators consider that minute|
differences in nuclie and cytoplasm are not as
clearly differentiated in tissue sections as in
2. Wet fixed smears.|
A thin of blood or other tissue
cells on a slide that is dropped into
the fixative before it dries. Usual
techniques from here on.
1. Cells by this method duplicate the ap+00A-|
pearance they have in fixed preparations so
that cells studied by either method can be
2. A fixing agent can be chosen that will|
serve a particular purpose--i. e., the use of
methyl alcohol for preservation of granules
in blood and tissue basophils.
3. Requires less them and equipment than|
the fixed-tissue method.
4. Cells usually not as severely flattened as|
in dry fixed smears.
1. Topographic relations with other cells|
and tissues are lost.
2. Cells do not show the delicate structural|
and tinctorial gradations seen in dry smears.
3. Has some practical disadvantages in the|
field, since it involves carrying a number of