The hams were sectioned through the body, the femur, or “middle bone,”
as it is known in packing-house parlance, being cut at a point about
1½ or 2 inches below its head. A cross section of a ham thus cut
is shown in figure 1. After sectioning, the hams were subjected to a
microscopical, bacteriological, and chemical examination as follows:
_Microscopical examination._—Bits of muscular tissue, taken from
various points, were teased out in salt solution and the condition of
the muscle fibers noted. Smear preparations were also made from bits
of muscular tissue and from the bone marrow, and these were stained
and subjected to microscopical examination. Portions of the meat were
also hardened and cut into microscopic sections, which were stained and
mounted for histological and bacteriological study.
_Bacteriological examination._—In the bacteriological examination
of sour hams, especial attention was directed to the detection of
anaerobic species, as it seemed reasonable to suppose that if the
changes taking place in sour hams were due to bacteria these bacteria
would in all likelihood be anaerobes (i. e., organisms which develop
in the absence of oxygen). This assumption was based upon the fact
that, as a rule, souring begins in the interior of the ham next to the
bone, and, furthermore, the hams are cured in large vats where they
are completely submerged in the pickling fluids, so that any bacteria
which develop within the bodies of the hams while they are in cure are
probably restricted to practically anaerobic conditions.
Cultures were made from the interiors of the hams at various points by
first searing the cut surface thoroughly with a heavy metal spatula and
then cutting out, by means of sterile scissors and forceps, plugs of
meat about 1 cm. square. The plugs of meat were then dropped into tubes
containing the egg-pork medium and pushed down to the bottom of the
tubes, where they were held in place by the chopped meat above; in this
way conditions favorable for the development of anaerobic organisms
were obtained. In inoculating the pork-agar tubes, the medium was
first boiled to expel any inclosed air and cooled to 43° to 45° C; the
plugs of meat were then dropped into the tubes and the agar rapidly
solidified by plunging the tubes in cold water; in this way the bits of
meat were inclosed in the agar at the bottom of the tubes, affording
suitable conditions for anaerobic growth. Aerobic and anaerobic plates
were also made from the meat, and in most cases bouillon tubes were
also inoculated. Cultures were always taken from the bone marrow as
well as from the meat. Novy jars were also used for obtaining anaerobic
conditions in growing the cultures.
_Chemical examination._—In order to determine whether the souring was
connected with or dependent upon a lack of penetration of the pickling
fluids to the interior of the meat, the hams were further subjected to
a chemical examination and the content of the meat in sodium chlorid
and potassium nitrate determined at varying depths.