362
Z. RYCHTER
ostium: the muscular flap (Fig. 26e, e'—cut at ventrocranial end)
vanished completely and two valves developed (Fig. 28c'), so that the
right venous ostium imitated the left one. In one case, three valves
occurred. An unexpected impulse thus emerged towards a revision of
the problem of the so-called inversion of the ventricles, classified
traditionally according to the atrioventricular valve morphology.
E. Influence of the Blood Stream on the Proximal Bulbar Cushions
In latter sections of this chapter, it has been demonstrated that the
changed haemodynamics can modify in various ways the development
of the distal and proximal bulbar cushions, especially the latter.
At the level of the proximal bulbar cushions, in the future pulmonary
portion of the heart bulb of chick embryos, a third small cushion was
described by Hochstetter (1906). Spitzer (1919, 1921, 1923) maintained
that, from the phylogenetic viewpoint, in man, it was a rudiment of the
septum which, in reptiles, originally separates the conus of the right
ventricular aorta.
The supposed importance of this structure (called perhaps not quite
suitably by Rychter (1959) the interstitial proximal cushion of the
heart bulb) led Rychter and Lemez (1960a) to study by microdissection
its frequency and life span, and its eventual bearing on bulbar septation
in normal development and under experimental conditions. In chick
embryos the interstitial proximal bulbar cushion was met with in the
pulmonary stream of the heart bulb (Fig. 13, Fig. 28b, Fig. 29—PIP)
from the stage of 4 days to that of 6 days 16 hr of incubation, using
20 embryos for each 4 hr of incubation. Its maximal frequency (50-70%)
occurred between 4 days 20 hr and 5 days 20 hr. Its size varied from a
FIG. 29. Diagrammatic horizontal section through the heart bulb at the level of right
and left ( P D and Ps) proximal bulbar cushions. Pip = proximal interstitial bulbar
cushion situated in the future pulmonary part of the bulb at 4 days and 20 hr of incubation.
Z. RYCHTER
ostium: the muscular flap (Fig. 26e, e'—cut at ventrocranial end)
vanished completely and two valves developed (Fig. 28c'), so that the
right venous ostium imitated the left one. In one case, three valves
occurred. An unexpected impulse thus emerged towards a revision of
the problem of the so-called inversion of the ventricles, classified
traditionally according to the atrioventricular valve morphology.
E. Influence of the Blood Stream on the Proximal Bulbar Cushions
In latter sections of this chapter, it has been demonstrated that the
changed haemodynamics can modify in various ways the development
of the distal and proximal bulbar cushions, especially the latter.
At the level of the proximal bulbar cushions, in the future pulmonary
portion of the heart bulb of chick embryos, a third small cushion was
described by Hochstetter (1906). Spitzer (1919, 1921, 1923) maintained
that, from the phylogenetic viewpoint, in man, it was a rudiment of the
septum which, in reptiles, originally separates the conus of the right
ventricular aorta.
The supposed importance of this structure (called perhaps not quite
suitably by Rychter (1959) the interstitial proximal cushion of the
heart bulb) led Rychter and Lemez (1960a) to study by microdissection
its frequency and life span, and its eventual bearing on bulbar septation
in normal development and under experimental conditions. In chick
embryos the interstitial proximal bulbar cushion was met with in the
pulmonary stream of the heart bulb (Fig. 13, Fig. 28b, Fig. 29—PIP)
from the stage of 4 days to that of 6 days 16 hr of incubation, using
20 embryos for each 4 hr of incubation. Its maximal frequency (50-70%)
occurred between 4 days 20 hr and 5 days 20 hr. Its size varied from a
FIG. 29. Diagrammatic horizontal section through the heart bulb at the level of right
and left ( P D and Ps) proximal bulbar cushions. Pip = proximal interstitial bulbar
cushion situated in the future pulmonary part of the bulb at 4 days and 20 hr of incubation.