300             'Lahore Canine Fever' and 'Tick Fever' of dogs

changes are noted. While mitosis and marked proliferation of the cells is
present, karryorhexis is evident in similar cells, the cytoplasm of which stains
faintly and appears as a mere rim around the disintegrating nucleus.

The majority of the cells present have clear, round nuclei, in which the
chromatin particles radiate from a central mass of nuclear chromatin. These
cells present themselves as typical reticular cells and similar cells are found
lining the spleen sinusoids. The second type of cell of numerical importance
is smaller than the foregoing. The nucleus is compact, deeply basophilic with
no internal structure. These are transitional lymphocytes and haemocytoblasts
(polyblasts). Interspersed with these are nucleated red blood cells in consi-
derable numbers. The venous sinuses are distended and the lining (littoral)
cells of the reticulo-endothelium show distinct mitosis. Many of the hyper-
plastic (macrophage) cells of the pulp contain blood pigment. A more import-
ant observation is that peculiar granules, staining intensely with Heidenhain's
iron haematoxylin, are found inside the cytoplasm of the polyblasts and reti-
cular cells. These granules are regular in size and appear in small well-defined
clusters. The nucleus of the cells in which they appear is distinct and free
from any degeneration. Similar forms, in larger clumps, may be found in
extracellular situations, as well as within the cytoplasm of the cells mentioned.
These forms stain indeterminately by the Romanowsky stains and judging by
a comparison of Heidenhain's stain on sections of the same tissue, it appears
that only a few of the bodies can be stained by this method. Pappenheim's
stain gives negative results. The changes of importance in the spleen may,
therefore, be summed up under three heads, intense and extensive cellular
hyperplasia, with the development of polyblasts and macrophages, haemato-
poiesis, and the appearance of peculiar, structureless inclusion bodies of small
size, both within and without the proliferating cells.

                                                LIVER

The changes in the liver are associated with an intense congestion. The
predominant feature is a reaction of the reticulo-endothelial cells lining the
sinusoids and the presence of blood pigment in these cells (cells of Kupffer)
which appear larger than normal. Necrosis and fatty degeneration is patchy
throughout the lobules and the appearance of an intense cellular infiltration
throughout, in some cases, suggests profound toxic excitation of the sub-
stance of the organ.

                                    THE BONE MARROW

The bone marrow shows changes similar to those described in the red
pulp of the spleen, with an erythropoiesis of an exaggerated degree. ' Inclu-
sion bodies ' are much more prominent than in the spleen and they are also
found in the haemocytoblasts.