December, 1954]
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organism. Quite likely, the parasite may be secreting some lytic enzyme, so far
unknown, in order to gain entry into the host cell. Even if it were so, the hydrolytic
mucopolysaccharide renders no insignificant service to its possessor for it has secured
a foothold for the organism and has created conditions ideal for enzymatic lysis.
There is again a great task of brisk physiological activity lying ahead of the
nucleus and cytoplasm of the parasite successively. Hyaluronic acid faithfully
accompanies the rise and depression in physiological activity. During the nuclear
division, it is present in nuclei in large quantities. At the approach of cessation
of nuclear division it totally disappears from this site and diffuses out into the
cytoplasm. At this time the sulphate-containing mucoid has also considerably
increased in concentration in the cytoplasm. Just prior to segmentation into mero-
zoites, this polysaccharide had condensed into numerous fine granules.
Fully formed merozoites contained hyaluronic acid in the cytoplasm in the
form of several granules lying just anterior to their nuclei. On rare occasions a
granule was also seen within the nucleus. At this very area there appeared several
metachromatic granules. This cytoplasmic region of the merozoite was also
rich in lipids since it reacted positively to neutral red (intravitam, Golgi element)
and turned black on osmication. It is very likely that the polysaccharides and
fats in this area exist in a mucolipid complex. It may be remembered that a com-
bination of these substances in bacteria is known to be strongly antigenic. At late
second generation schizogony, when mucopolysaccharides are present in abundance,
the parasite develops its immunogenic character. Thus it is quite likely that these
substances may be forming an important part of antigenic structure of the proto-
zoon.
Just before merozoite formation, i.e. on the late fourth day of infection, profuse
bleeding starts from blood vessels in sub-epithelial tissue where swarms of schizonts
have developed. At this stage of infection there is a heavy infiltration of caecal
tissue by mast cells which are known to manufacture heparin [Holmgren and Wilan-
der, 1937] and histamine [Riley, 1953]. Therefore, it can be safely presumed that
the heparin (a powerful anticoagulant) and histamine (the liberation of which in
body produces 'shock') [Abel and Kubola, 1919 ; Sherwood, et al., 1941] content
of the tissue is very high. This presumption receives substantial support from the
high anti-coagulant activity of pathological tissues rich in mast cells [Oliver, et al.,
1947, Ehrich, et al., 1949]. Heparin in caecal tissue may aid profuse local haemor-
rhage, and be responsible for the uncoagulated state of blood in caecal pouches in
E. tenella infection. Release of histamine in caecal tissue may aggravate the patho-
logical effect of the disease. But at this time the exudate present in the cæcal
pouch and mucosa contains a high concentration of a powerful thromboplastin
which when injected in as small a quantity as 0.5 ml. invariably killed healthy
chicks weighing over 800 gm. due to intravascular clotting [Bradford, et al., 1948].
This thromboplastic effect present in cæcal contents on 5th to 13th day after infec-
tion (due to E. tenella) may either be ascribed to excessive mobilisation of throm-
boplastin [Shaffiroff, et al., 1943] or it may be the result of severe hæmorrhage [van
den Valden, 1909 ; Grey and Lunt, 1914]. It may also be stated here, that in caecal
coccidiosis the loss of blood may be as high as 37 per cent [Pratt, 1938]. Thus,
the second generation merozoites have tough and trying time. They are bathed