346
Z. RYCHTER
right ventricular blood stream was also observed in 4 S , prolonging the
existence of this arch by 24 hr in the case of 6 D and by 48 hr in the case
of 6s as compared with normal development, thus confirming the greater
FIG. 14. The position of the primitive elastic tract (in black) (after Menkes, 1958).
Right side aspect. Ao = aorta; Tr = heart trunk; arrow indicates direction of blood flow.
haemodynamic significance of 6 S . Doubtless, the delay in the disappearance of 4 S led to the production of a cord from 4 S (Fig. 12a, b) in
about 30% of the embryos. No septal defects were found in the last
experiment.
Although, after suppression of both pulmonary arches, in some cases a
thin stream of blood from the right ventricle also reached both of the
3rd aortic arches, after elimination of 6D6S4S (Fig. 6), neither of the 3rd
aortic arches developed an additional arcus aortae. In this condition,
the aberrant right ventricular blood stream evidently comes into conflict
with another morphogenetic factor, which is thought to be connected
with the lengthening of the neck between the level of the 3rd and 4th
aortic arches, as indicated by the final position of the clips. During later
development those used for suppression of the 3rd aortic arches are
usually localized under the beak, those eliminating the 4th aortic
arches are found in the caudal part of the neck, and those eliminating
the 6th are found in the chest (Rychter and Lemez, unpublished data).
Moffat (1959) explains the disappearance of the ductus caroticus in
rat embryos by changes in the direction of the blood stream in this
region.
The preceding observations show that the influence of morphogenetic
factors should be judged not in isolation, but always in their mutual
relations. Research into congenital malformations has been greatly
retarded by the abundance of different theories promoting speculatively
a detail or morphogenetic factor to an all-explaining cause with undialectic disregard for the complex frame of nature.
Z. RYCHTER
right ventricular blood stream was also observed in 4 S , prolonging the
existence of this arch by 24 hr in the case of 6 D and by 48 hr in the case
of 6s as compared with normal development, thus confirming the greater
FIG. 14. The position of the primitive elastic tract (in black) (after Menkes, 1958).
Right side aspect. Ao = aorta; Tr = heart trunk; arrow indicates direction of blood flow.
haemodynamic significance of 6 S . Doubtless, the delay in the disappearance of 4 S led to the production of a cord from 4 S (Fig. 12a, b) in
about 30% of the embryos. No septal defects were found in the last
experiment.
Although, after suppression of both pulmonary arches, in some cases a
thin stream of blood from the right ventricle also reached both of the
3rd aortic arches, after elimination of 6D6S4S (Fig. 6), neither of the 3rd
aortic arches developed an additional arcus aortae. In this condition,
the aberrant right ventricular blood stream evidently comes into conflict
with another morphogenetic factor, which is thought to be connected
with the lengthening of the neck between the level of the 3rd and 4th
aortic arches, as indicated by the final position of the clips. During later
development those used for suppression of the 3rd aortic arches are
usually localized under the beak, those eliminating the 4th aortic
arches are found in the caudal part of the neck, and those eliminating
the 6th are found in the chest (Rychter and Lemez, unpublished data).
Moffat (1959) explains the disappearance of the ductus caroticus in
rat embryos by changes in the direction of the blood stream in this
region.
The preceding observations show that the influence of morphogenetic
factors should be judged not in isolation, but always in their mutual
relations. Research into congenital malformations has been greatly
retarded by the abundance of different theories promoting speculatively
a detail or morphogenetic factor to an all-explaining cause with undialectic disregard for the complex frame of nature.