There is ample evidence that both the lymphadenoid and myeloid tissues
of the body are affected. The lymph glands at the hilum of the lung
naturally are involved with the extensive pulmonary changes. Also, a
similar change may be found in distant nodes, perhaps associated with
drainage from focal lesions or perhaps brought about by general
intoxication.
The myeloid involvement is unassociated with focal lesions and finds its
early expression in the equation of the white blood cells of the
peripheral blood. The two groups of changes, those involving the
lymphadenoid and those of the myeloid structures, should be discussed
separately.
_Lymphadenoid Tissues._
By far the most extensive lesions are encountered in the lymph glands of
the lung and its hilum, and from here the mediastinal and deep nodes
along the trachea are affected to a greater or lesser extent. The glands
are very large and succulent (2, 157, 162, etc.). Very frequently,
indeed, they are hemorrhagic on cross section (34, 108) (Fig. XXXVII),
and there exudes a sanguinous fluid, usually thin and syrupy in
character. The cut surface projects slightly, and the edge of the gland
everts. The architecture is often obscured by hemorrhage—a diffuse red
color—but very frequently near the periphery, translucent or more
opaque, yellowish points are visible. Rarely, larger, opaque, yellow
foci are found in the gland; these may be softened and purulent in
exceptional cases (2, 47, 157).
Microscopically, the picture presented by the gland is that of a
non-suppurative lymphadenitis. The peripheral sinuses are markedly
distended and the channels through the gland share in the change (66).
The sinuses contain serum, red blood cells, and mononuclear cells for
the most part, but occasionally polymorphonuclear leucocytes are also
encountered. More rarely still, a megalokaryocyte finds its way into the
sinus. The most characteristic feature is the presence of phagocytosed
cells,—a picture comparable with that found in the typhoid lymph node.
The nuclei of the phagocytic cells are vesicular and usually stand out
sharply in contrast with the pyknotic nuclei of the included cells.
There is conclusive evidence that the phagocytes arise from the lining
cells of the channel wall, as in typhoid fever, for these cells are
frequently in process of division (Fig. LIV). The blood vessels of the
lymph gland, greatly congested, contain almost exclusively red blood
cells. As a rule, the lymph follicles and the lymph cords take little
part in the process. If there is any change in these structures, it is a
rarefication. Occasionally, hemorrhage is encountered in a follicle or
even in a cord, and this hemorrhage may involve not only the cells of
the cord, but its supporting reticular structure, and may form the
nucleus of a subsequent necrotizing or suppurative focus.
[Illustration:
FIG. XXXI. AUTOPSY NO. 100. ACUTE FULMINATING BRONCHIOLITIS AND
BRONCHOPNEUMONIA. NOTE THE NECROTIC ALVEOLAR WALLS AND THE MASSES OF
BACTERIA IN THE EXUDATE. COMPARE FIGURES VIII, XVII, AND XXXII.
]
The picture that has been detailed is subject to modification in those
cases particularly where a leucocytic reaction is associated. Then,
there may be more polymorphonuclear leucocytes in the sinuses, and
necrotizing foci may be converted into miliary abscesses.
The change in the bronchial lymph glands cannot be considered other than
an expression of an aplastic, inflammatory reaction. It finds an
analogue especially in diseases like typhoid fever. The most constant
picture includes an edematous, hemorrhagic reaction in which there is
phagocytosis of sieved-out cells by the scavengers generated within the
gland. Where necrosis or suppuration occurs, and this is rare, it may be
considered as a complication.
Elsewhere in the body, the lymph glands rarely show the same degree of
change as those of the thorax. The same general picture, however, is
present to a greater or lesser extent, except that extensive necrosis
and suppuration have not been encountered.
The lymphadenoid tissues of the alimentary canal share in the process
only to a minor extent. In a number of cases, there is no question that
the Peyer’s patches and solitary follicles are hyperplastic. Grossly,
they stand out prominently, and are pale pinkish-grey in color.
Histologically, there is hyperplasia, chiefly apparent from the large
germinal centers in the follicles, and a slight distention of the lymph
channels. This picture, so commonly found in every type of general
infection, is in no way characteristic of influenza.
_Spleen._
The spleen is the seat of the usual manifestations in generalized acute
infections. In no case is the organ markedly involved, although
considerable increases in its size may occur (2, 108, 141, 157, 162). It
is not feasible to introduce a detailed discussion of this mild grade of
splenic tumor, for there are natural variations in the size of the
spleen and frequently it is modified in this respect by subsidiary
conditions. In every instance the capsule of the spleen is smooth and
there is no acute or chronic perisplenitis attributable to influenza.
The capsule usually retracts slightly and the splenic pulp, in slight
excess, is much more frequently red or garnet than grey in color.
Occasionally, the splenic tumor is grey as in pneumonia. The more minute
changes in the organ consist of congestion of the sinuses, increase of
the mononuclear cells of the pulp, and prominence of the germinal
centers of the Malpighian corpuscles (140). Hemorrhages, found
occasionally (47), are more frequent in the pulp, but also occur in the
corpuscles.
_Bone Marrow._
One of the clinical features of influenza is a leukopenia, which
persists often in the face of acute pyogenic pulmonary infection (12,
138, 143, etc.). In this series of ninety-five cases, the vast majority
had this type of blood picture, but occasionally a leucocytosis (14) was
demonstrable even during the early part of the disease and in those
cases which terminated fatally within a period that may be called acute.
In almost all instances where fatal termination was delayed, the
leucocyte count ultimately was elevated either with remission or to a
constant high level. The blood studies have not been sufficiently
complete to allow further discussion, though there is reason to believe
that these might have yielded interesting results. The blood changes in
this series are similar to those presented in the reports of the
epidemic from other sources.
In the majority of cases where the marrow was studied, it was aplastic
(12). Occasional, focal, hemorrhagic lesions of the marrow (47) similar
to those discussed below in the skeletal and parenchymatous systems were
encountered and there was an apparent increase in the number of
megalokaryocytes. The usual hyperplasia of the myeloid elements of the
marrow associated with pyogenic change was not present.