the haemolyrnph and cwncentrate them in ampullae or tubules. In this
respect the gland may be considered to have an excretory function but
it does not imply that this i F its primary role.
The presence of R holocrine secr4,ion in th(. gland and the undoubted
fact that in many, if not all, specks there are cilia in the pyloric duct
which beat towards the gastro-intestinal junction, suggests that a
part of the function of the gland is to discharge some substance into the
alimentary ctinal. Prom the point of view of digestive physiology this
region of the canal is the most active and critical of all, the region where
enzymes and food are being mixed and prior to the main site of absorption. It seems inconceivabl(~ that any true excretory organ would
discharge at such a plt~c*e and som(L other function is more likely. It is a
region in which one might oxpect digrstive enzymes to be discharged
but all the available evidence a t present suggests that the stomach is
the sole site of production of digestive enzymes. If the pyloric gland
was producing notable quantities of digestive enzymes they should be
identifiable in homogenates of the intestine, but they have not been
identified there (Yonge, 1925; Berrill, 1929; Van Weel, 1940). Fouque
(1954) dismisses the idea that the gland may secrete digestive enzymes
on the grounds that the duct is not always open but this may be an
abnormal phenomenon. Berrill (1950) on the other hand put forward a
novel suggestion that the gland was uscd to recover enzymes from the
intestine. However, in an earlier paper (Rerrill, 1929) he suggested that
the timing of passage of food through the alimentary canal was adjusted
to make maximum 1182: of the cmzyrnes during slow passage through the
intestine. If this is truc then tttiy Bystern for eiizyme recovery should be
concentrated in the posterior part of thc intestine, but the work of
Fouque (1!$54) suggests that the most wtiw region of the gland i H
around the n,id-intestioc.. Fitrthermore, any hystem of recovery would
require a mec*hrtnism for re-tibsorbiiig large protein molcculeh.
According to Fouque the intc.ntina1 epithelium in the neighhourhood
of the ampulltre is modified and thcrt: appearH to 1)c s n intimate tmocintion between the two. Fouque considered that the ampullae are
engaged in a “ re-working ” process of xubRtanceH which are absorbed
by the intestinal cells, passed on to the cells of the ampulla which
further treats them and subsequently passes the re-worked material
back to the parapyloric cells which play the role of trophocytes. In view
of the holocrine nature of the ampullary epithelium and the fact that
vital dyes such as indigocannine, neutral red, methylene blue and
toluidine blue are picked up from the haemolymph and concentrated
in the ampullae and tubules (Fouque, 1954; Godeaux, 1954) it seems
unlikely that metabolites are treated in this way by the gland. Active
respect the gland may be considered to have an excretory function but
it does not imply that this i F its primary role.
The presence of R holocrine secr4,ion in th(. gland and the undoubted
fact that in many, if not all, specks there are cilia in the pyloric duct
which beat towards the gastro-intestinal junction, suggests that a
part of the function of the gland is to discharge some substance into the
alimentary ctinal. Prom the point of view of digestive physiology this
region of the canal is the most active and critical of all, the region where
enzymes and food are being mixed and prior to the main site of absorption. It seems inconceivabl(~ that any true excretory organ would
discharge at such a plt~c*e and som(L other function is more likely. It is a
region in which one might oxpect digrstive enzymes to be discharged
but all the available evidence a t present suggests that the stomach is
the sole site of production of digestive enzymes. If the pyloric gland
was producing notable quantities of digestive enzymes they should be
identifiable in homogenates of the intestine, but they have not been
identified there (Yonge, 1925; Berrill, 1929; Van Weel, 1940). Fouque
(1954) dismisses the idea that the gland may secrete digestive enzymes
on the grounds that the duct is not always open but this may be an
abnormal phenomenon. Berrill (1950) on the other hand put forward a
novel suggestion that the gland was uscd to recover enzymes from the
intestine. However, in an earlier paper (Rerrill, 1929) he suggested that
the timing of passage of food through the alimentary canal was adjusted
to make maximum 1182: of the cmzyrnes during slow passage through the
intestine. If this is truc then tttiy Bystern for eiizyme recovery should be
concentrated in the posterior part of thc intestine, but the work of
Fouque (1!$54) suggests that the most wtiw region of the gland i H
around the n,id-intestioc.. Fitrthermore, any hystem of recovery would
require a mec*hrtnism for re-tibsorbiiig large protein molcculeh.
According to Fouque the intc.ntina1 epithelium in the neighhourhood
of the ampulltre is modified and thcrt: appearH to 1)c s n intimate tmocintion between the two. Fouque considered that the ampullae are
engaged in a “ re-working ” process of xubRtanceH which are absorbed
by the intestinal cells, passed on to the cells of the ampulla which
further treats them and subsequently passes the re-worked material
back to the parapyloric cells which play the role of trophocytes. In view
of the holocrine nature of the ampullary epithelium and the fact that
vital dyes such as indigocannine, neutral red, methylene blue and
toluidine blue are picked up from the haemolymph and concentrated
in the ampullae and tubules (Fouque, 1954; Godeaux, 1954) it seems
unlikely that metabolites are treated in this way by the gland. Active