282
AUGUST EPPLE
to the intestinal tract at the transition from foregut to midgut; in the
adult animal, the ventral portion also extends into the liver (Ermisch,
1966). In Myxine and Bddlostomu, the islet tissue surrounds the bile duct
( Schirner, 1963a; Falkmer and Winbladh, 1964a).
The exocrine pancreas of the cyclostomes is separated entirely from
the islet tissue. According to Schirner (1963a,b), it consists in Myxine and
BdeZZostomu ( 1) of zymogen cells in the intestinal epithelium, (2) of an
intrahepatic portion, and (3) of scattered elements in the ligamentum
hepatogastricum. According to Luppa and Ermisch ( 1967), the exocrine
pancreas of Petromyzon and Myxine is represented only by specialized
cells of the intestinal epithelium.
Using modern methods, Ermisch (1966) and Winbladh (1966) recently studied the endocrine pancreas of Petromyzon pluneri and Petromyzon fluuiatilis. There are B cells, aldehydefuchsin-negative granular
cells, and a few agranular cells. The function of the aldehydefuchsinnegative granular cells is obscure. Apparently, their granules appear at the
electron microscopic level as empty vesicles ( Winbladh, 1966). The
agranular cells probably represent undifferentiated precursors of both
types of granular cells (Ermisch, 1966). Both types of granular cells are
largely restricted to islets of their own. In larval specimens of Petromyzon
phneri, the lobules consist almost exclusively of B cells, whereas in the
adult animals the percentage of B cells drops about 4%! %
(Ermisch,
1966). The islets of adult Petromyzon fluviatilis contain about 33% B cells
( Winbladh, 1966). The cavities of the lobules contain a colloid and
sometimes also cell debris ( Winbladh, 1966) ; from histochemical findings,
Ermisch (1967) postulates the occurrence of insulin; B cells may also
contain colloid droplets.
The cytology in Myxine is similar to Petromyzon. B cells make up
two-thirds of the islet cells, whereas the rest consists mainly of “agranular”
cells ( Falkmer and Winbladh, 1964a). However, ultrastructurally they
contain empty vesicles and thus appear to correspond to the second type
of granular cells of Petromyzon (Winbladh, 1Qf36). The content of the
lobule cavities in Myxine apparently is the same as in Petromqzon
( Schirner, 1963a; Falkmer and Winbladh, 1964a).
Schirner (1963a,b) reports the occurrence of A cells in the Myxinidae.
These elements could not be identified histochemically and ultrastructurally by other investigators in Petromyzon and in Myxine (Ermisch,
1966; Falkmer and Winbladh, 1964a; Winbladh, 1966).
Histochemically, the B cells of the lampreys contain glycogen and zinc.
The reaction for zinc is strong in Petromyzon fluviatilis and weak in
Petromyzon phneri ( Ermisch, 1966). In Myxine, zinc is practically absent
(Falkmer and Winbladh, 1964a; Pihl, 1967).
AUGUST EPPLE
to the intestinal tract at the transition from foregut to midgut; in the
adult animal, the ventral portion also extends into the liver (Ermisch,
1966). In Myxine and Bddlostomu, the islet tissue surrounds the bile duct
( Schirner, 1963a; Falkmer and Winbladh, 1964a).
The exocrine pancreas of the cyclostomes is separated entirely from
the islet tissue. According to Schirner (1963a,b), it consists in Myxine and
BdeZZostomu ( 1) of zymogen cells in the intestinal epithelium, (2) of an
intrahepatic portion, and (3) of scattered elements in the ligamentum
hepatogastricum. According to Luppa and Ermisch ( 1967), the exocrine
pancreas of Petromyzon and Myxine is represented only by specialized
cells of the intestinal epithelium.
Using modern methods, Ermisch (1966) and Winbladh (1966) recently studied the endocrine pancreas of Petromyzon pluneri and Petromyzon fluuiatilis. There are B cells, aldehydefuchsin-negative granular
cells, and a few agranular cells. The function of the aldehydefuchsinnegative granular cells is obscure. Apparently, their granules appear at the
electron microscopic level as empty vesicles ( Winbladh, 1966). The
agranular cells probably represent undifferentiated precursors of both
types of granular cells (Ermisch, 1966). Both types of granular cells are
largely restricted to islets of their own. In larval specimens of Petromyzon
phneri, the lobules consist almost exclusively of B cells, whereas in the
adult animals the percentage of B cells drops about 4%! %
(Ermisch,
1966). The islets of adult Petromyzon fluviatilis contain about 33% B cells
( Winbladh, 1966). The cavities of the lobules contain a colloid and
sometimes also cell debris ( Winbladh, 1966) ; from histochemical findings,
Ermisch (1967) postulates the occurrence of insulin; B cells may also
contain colloid droplets.
The cytology in Myxine is similar to Petromyzon. B cells make up
two-thirds of the islet cells, whereas the rest consists mainly of “agranular”
cells ( Falkmer and Winbladh, 1964a). However, ultrastructurally they
contain empty vesicles and thus appear to correspond to the second type
of granular cells of Petromyzon (Winbladh, 1Qf36). The content of the
lobule cavities in Myxine apparently is the same as in Petromqzon
( Schirner, 1963a; Falkmer and Winbladh, 1964a).
Schirner (1963a,b) reports the occurrence of A cells in the Myxinidae.
These elements could not be identified histochemically and ultrastructurally by other investigators in Petromyzon and in Myxine (Ermisch,
1966; Falkmer and Winbladh, 1964a; Winbladh, 1966).
Histochemically, the B cells of the lampreys contain glycogen and zinc.
The reaction for zinc is strong in Petromyzon fluviatilis and weak in
Petromyzon phneri ( Ermisch, 1966). In Myxine, zinc is practically absent
(Falkmer and Winbladh, 1964a; Pihl, 1967).